Verification of cardiac arrhythmia prior to therapeutic stimulation

ABSTRACT

Ambulatory medical devices may occasionally improperly administer a therapeutic stimulation pulse to a patient upon an incorrect detection of arrhythmia in the patient. To address these improperly administered therapeutic stimulation pulses, an ambulatory medical device includes processes and systems for verifying an initial declaration of an arrhythmia. The ambulatory medical device described include at least one first sensing electrode and at least one second sensing electrode distinct from the at least one first sensing electrode. First electrocardiogram (ECG) signals detected by the first sensing electrode are analyzed to provide an initial declaration of the arrhythmia condition of the patient. As a treatment protocol is being initiated in response to the analysis of the first ECG signals, second ECG signals detected by the second sensing electrode are analyzed to verify the initial declaration of the arrhythmia.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/917,982 (filed 12 Mar. 2018), the entire disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND

The present disclosure is related to detection of abnormal cardiacevents and treatment of cardiac arrhythmias.

There are a wide variety of electronic and mechanical devices formonitoring and treating patients' medical conditions. In some examples,depending on the underlying medical condition being monitored ortreated, medical devices such as cardiac monitors or defibrillators maybe surgically implanted or externally connected to the patient. In somecases, physicians may use medical devices alone or in combination withdrug therapies to treat conditions such as cardiac arrhythmias.

One of the deadliest cardiac arrhythmias include ventricularfibrillation, which occurs when normal, regular electrical impulses arereplaced by irregular and rapid impulses, causing the heart muscle tostop normal contractions. Normal blood flow ceases, and organ damage ordeath can result in minutes if normal heart contractions are notrestored. Because the victim has no perceptible warning of the impendingfibrillation, death often occurs before the necessary medical assistancecan arrive. Other cardiac arrhythmias can include excessively slow heartrates known as bradycardia or excessively fast heart rates known astachycardia. Cardiac arrest can occur when a patient in which variousarrhythmias of the heart, such as ventricular fibrillation (VF),ventricular tachycardia (VT), pulseless electrical activity (PEA), andasystole (heart stops all electrical activity) result in the heartproviding insufficient levels of blood flow to the brain and other vitalorgans for the support of life.

Cardiac arrest and other cardiac health ailments are a major cause ofdeath worldwide. Various resuscitation efforts aim to maintain thebody's circulatory and respiratory systems during cardiac arrest in anattempt to save the life of the patient. The sooner these resuscitationefforts begin, the better the patient's chances of survival. Implantablecardioverter/defibrillators (ICDs) or external defibrillators (such asmanual defibrillators or automated external defibrillators (AEDs)) havesignificantly improved the ability to treat these otherwiselife-threatening conditions. Such devices operate by applyingtherapeutic stimulation pulses directly to the patient's heart.Ventricular fibrillation or ventricular tachycardia can be treated by animplanted or external defibrillator, for example, by providing atherapeutic shock to the heart in an attempt to restore normal rhythm.To treat conditions such as bradycardia, an implanted or external pacingdevice can provide pacing stimuli to the patient's heart until intrinsiccardiac electrical activity returns.

Example external cardiac monitoring and/or treatment devices includecardiac monitors, the ZOLL® LifeVest® wearable cardioverterdefibrillator available from ZOLL® Medical Corporation, and the AED Plusalso available from ZOLL® Medical Corporation.

SUMMARY

In at least one example, an ambulatory medical device is provided. Theambulatory medical device includes a pair of therapy electrodes; firstand second pairs of sensing electrodes, and at least one processorcoupled to the pair of therapy electrodes and the first and second pairsof sensing electrodes. The pair of therapy electrodes is configured tocouple externally to a skin of a patient and to provide one or moretherapeutic stimulation pulses to a heart of the patient duringexecution of a treatment protocol. The first pair of sensing electrodesis configured to couple externally to the skin of the patient and toacquire first electrocardiogram (ECG) signals. The second pair ofsensing electrodes is distinct from the first pair of sensing electrodesand is configured to couple externally to the skin of the patient toacquire second ECG signals having an improved reliability over the firstECG signals. The at least one processor is configured to receive firstECG data generated from the first ECG signals; analyze the first ECGdata to detect an arrhythmia condition of the patient; record an initialdeclaration of the arrhythmia condition of the patient in response todetecting the arrhythmia condition; initiate the treatment protocol inresponse to the initial declaration of the arrhythmia condition; receivesecond ECG data generated from the second ECG signals; and analyze thesecond ECG data to verify the initial declaration of the arrhythmiacondition.

In the ambulatory medical device, the at least one processor may befurther configured to abort the treatment protocol in response todetecting normal cardiac function based on analysis of the second ECGdata. The at least one processor may be further configured to controldelivery of the one or more therapeutic stimulation pulses to the heartof the patient in response to verifying the initial declaration of thearrhythmia condition.

In the ambulatory medical device, the first pair of sensing electrodesmay include dry sensing electrodes. The second pair of sensingelectrodes may include an electrically conductive sensing elementconfigured to be electrically coupled to the skin of the patient via aconductive gel.

The ambulatory medical device may further include a gel dispenser. Thegel dispenser may be configured to dispose gel between an electricallyconductive element of the second pair of sensing electrodes and the skinof the patient. The ambulatory medical device may further include geldeployment circuitry coupled to the at least one processor, and the atleast one processor may be further configured to signal the geldeployment circuitry to cause at least one gel dispenser to applyconductive gel between the skin of the patient and the second pair ofsensing electrodes in response to detecting the arrhythmia condition andprior to acquiring the second ECG signals.

The ambulatory medical device may further include a pair of electrodeassemblies including the second pair of sensing electrodes and the atleast one gel dispenser. The ambulatory medical device may furtherinclude a pair of therapy pads including the at least one gel dispenserand the pair of therapy electrodes. The pair of therapy electrodes mayinclude the second pair of sensing electrodes.

In the ambulatory medical device, the at least one processor may beconfigured to analyze the first ECG data with an abnormality detectionprocess and to analyze the second ECG data with an arrhythmiaverification process. The ambulatory medical device may further includeat least one non-ECG sensor, the at least one non-ECG sensor includingone or more of an accelerometer and a photoplethysmograph sensor. The atleast one processor may be further coupled to the at least one non-ECGsensor and be further configured to receive non-ECG data generated fromsignals acquired by the at least one non-ECG sensor; and analyze thenon-ECG data with the abnormality detection process to contribute todetection of the arrhythmia condition.

In another example, another ambulatory medical device is provided. Thisambulatory medical device includes a pair of sensing electrodes, a pairof multi-function electrodes, and at least one processor coupled to thepair of sensing electrodes and the pair of multi-function electrodes.The pair of sensing electrodes is configured to couple externally to askin of a patient and to acquire first electrocardiogram (ECG) signalsto detect an arrhythmia condition of the patient. The pair ofmulti-function electrodes is configured to couple externally to the skinof the patient and to provide one or more therapeutic stimulation pulsesto a heart of the patient during execution of a treatment protocol andto acquire second ECG signals to verify the arrhythmia condition of thepatient. The at least one processor is coupled to the pair of sensingelectrodes and the pair of multi-function electrodes and is configuredto receive first ECG data generated from the first ECG signals; analyzethe first ECG data to detect the arrhythmia condition of the patientusing an abnormality detection process; record an initial declaration ofthe arrhythmia condition of the patient in response to detecting thearrhythmia condition; initiate the treatment protocol in response to theinitial declaration; receive second ECG data generated from the secondECG signals; and analyze the second ECG data to either verify or refutethe initial declaration of the arrhythmia condition using an arrhythmiaverification process distinct from the abnormality detection process.

In the ambulatory medical device, the at least one processor may befurther configured to delay the treatment protocol in response torefuting the initial declaration of the arrhythmia condition. The atleast one processor may be further configured to abort the treatmentprotocol in response to determining that normal rhythm has returned inthe patient. The at least one processor may be further configured tocontrol delivery of the one or more therapeutic stimulation pulses tothe heart of the patient in response to verifying the initialdeclaration of the arrhythmia condition.

The ambulatory medical device may further include gel deploymentcircuitry coupled to the at least one processor. The at least oneprocessor may be further configured to signal the gel deploymentcircuitry to cause at least one gel dispenser to apply conductive gelbetween the skin of the patient and the pair of multi-functionelectrodes in response to detecting the arrhythmia condition and priorto acquiring the second ECG signals.

The ambulatory medical device may further include a pair of electrodeassemblies including the pair of multi-function electrodes and the atleast one gel dispenser. The ambulatory medical device may furtherinclude a pair of therapy pads including the at least one gel dispenserand a pair of therapy electrodes, wherein the pair of multi-functionelectrodes comprise the pair of therapy electrodes.

The ambulatory medical device may further include at least one non-ECGsensor. The at least one non-ECG sensor may include one or more of anaccelerometer and a photoplethysmograph sensor. The at least oneprocessor may be further coupled to the at least one non-ECG sensor andbe further configured to receive non-ECG data generated from signalsacquired by the at least one non-ECG sensor and analyze the non-ECG datausing the abnormality detection process to contribute to detection ofthe arrhythmia condition.

In another example, another ambulatory medical device is provided. Theambulatory medical device includes a pair of therapy electrodes, firstand pairs of sensing electrodes, gel deployment circuitry, and at leastone processor coupled to the first and second pairs of sensingelectrodes, the pair of therapy electrodes, and the gel deploymentcircuitry. The pair of therapy electrodes is configured to coupleexternally to a skin of a patient and to provide one or more therapeuticstimulation pulses to a heart of the patient during execution of atreatment protocol. The first pair of sensing electrodes is configuredto couple externally to the skin of the patient and to acquire firstelectrocardiogram (ECG) signals. The second pair of sensing electrodesis distinct from the first pair of sensing electrodes and is configuredto couple externally to the skin of the patient and to acquire secondECG signals. The at least one processor is coupled to the first pair ofsensing electrodes, the second pair of sensing electrodes, the pair oftherapy electrodes, and the gel deployment circuitry and is configuredto receive first ECG data generated from the first ECG signals, analyzethe first ECG data to detect an arrhythmia condition of the patient,record an initial declaration of the arrhythmia condition of the patientin response to detecting the arrhythmia condition, initiate thetreatment protocol in response to the initial declaration of thearrhythmia condition, signal the gel deployment circuitry to cause atleast one gel dispenser to apply conductive gel between the second pairof sensing electrodes and the skin of the patient prior to acquiring thesecond ECG signals, receive second ECG data generated from the secondECG signals, analyze the second ECG data to verify the initialdeclaration of the arrhythmia condition, either abort or delay thetreatment protocol in response to at least one of detecting normalcardiac function and refuting the initial declaration of the arrhythmiacondition based on analysis of the second ECG data, and control deliveryof the one or more therapeutic stimulation pulses to the heart of thepatient in response to verifying the initial declaration of thearrhythmia condition.

In the ambulatory medical device, the first pair of sensing electrodesmay include dry sensing electrodes. The second pair of sensingelectrodes may include conductive sensing electrodes.

In another example, another ambulatory medical device is provided. Theambulatory medical device includes a pair of therapy electrodes, a pairof sensing electrodes, ECG sensing electrode circuitry coupled to thepair of sensing electrodes, and at least one processor coupled to thepair of sensing electrodes, the ECG sensing electrode circuitry, and thepair of therapy electrodes. The pair of therapy electrodes is configuredto couple externally to a skin of a patient and to provide at least onetherapeutic stimulation pulse to a heart of the patient. The pair ofsensing electrodes is configured to couple externally to the skin of thepatient and to acquire first and second of electrocardiogram (ECG)signals from the patient. The ECG sensing electrode circuitry isconfigured to process the acquired first and second ECG signals from thepatient to generate first and second ECG data. The at least oneprocessor is and configured to receive the first ECG data; analyze thefirst ECG data using a first process to detect an arrhythmia conditionof the patient; record an initial declaration of the arrhythmiacondition of the patient in response to detecting the arrhythmiacondition; initiate a treatment protocol in response to the initialdeclaration of the arrhythmia condition, the treatment protocolspecifying provision of at least one alarm indicating an imminentdelivery of at least one therapeutic stimulation pulse and provision ofthe at least one therapeutic stimulation pulse; cause the ECG sensingelectrode circuitry to activate a second process distinct from the firstprocess to analyze the second ECG signals; receive the second ECG data;and analyze, after the provision of the at least one alarm and beforethe provision of the at least one therapeutic stimulation pulse, thesecond ECG data using the second process distinct from the first processto verify the initial declaration of the arrhythmia condition.

In the ambulatory medical device, the second process may be configuredto have improved reliability in analyzing the second ECG signals toverify the initial declaration of the arrhythmia condition. The at leastone processor may be further configured to control delivery of the atleast one therapeutic stimulation pulse in response to verifying theinitial declaration of the arrhythmia condition. The at least oneprocessor may be further configured to refute, using the second ECGdata, the initial declaration of the arrhythmia condition and delay theprovision of the at least one therapeutic stimulation pulse in responseto refuting the initial declaration of the arrhythmia condition. Thedelay may include a delay having a duration between 30 seconds and 45seconds. The at least one processor may be configured to analyze thesecond ECG data using the second process at least in part by determininga value that indicates a confidence that the second ECG data reflectsnormal cardiac function of the patient and evaluate the value. The atleast one processor may be configured to evaluate the value at least inpart by comparing the value to a threshold value.

In ambulatory medical device, the first process may include anabnormality detection process, and the second process may include anarrhythmia verification process. The abnormality detection process mayinclude a first number of sub-processes, and the arrhythmia verificationprocess may include a second number of sub-processes less than the firstnumber of sub-processes. The abnormality detection process may include afirst set of sub-processes, and the arrhythmia verification process mayinclude a second set of sub-processes different than the first set ofsub-processes. The arrhythmia verification process may include at leastone of a heart rate detection sub-process and a signal morphologydetection sub-process. The abnormality detection process may include afirst fast Fourier transform, and the arrhythmia verification processmay omit a second fast Fourier transform.

In the ambulatory medical device, the at least one processor isconfigured to cause the ECG sensing electrode circuitry to activate thesecond process to analyze the second ECG signals within of a predefinedperiod of time after the initial declaration of the arrhythmiacondition. The predefined period of time may have a duration inclusivelybetween 1 and 60 seconds. The predefined period of time may varies basedon the arrhythmia condition. Where the arrhythmia condition isventricular tachycardia, the predefined period of time may include 8 to10 seconds. Where the arrhythmia condition is ventricular fibrillation,the predefined period of time may include 5 to 8 seconds.

The ambulatory medical device may further include at least one non-ECGsensor. The at least one non-ECG sensor may include one or more of anaccelerometer and a photoplethysmograph sensor. The at least oneprocessor may be further coupled to the at least one non-ECG sensor andmay be further configured to receive non-ECG data generated from signalsacquired by the at least one non-ECG sensor and analyze the non-ECG datawith the abnormality detection process to contribute to detection of thearrhythmia condition. The ambulatory medical device may further includea garment housing the pair of sensing electrodes and the second processmay include a process to tighten the garment around the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of one or more examples are discussed below withreference to the accompanying drawings, which are not intended to bedrawn to scale. The drawings are included to provide an illustration anda further understanding of these various aspects and examples. Thedrawings are incorporated in and constitute a part of this specificationbut are not intended to limit the scope of the disclosure. The drawings,together with the remainder of the specification, serve to explainprinciples and operations of the described and claimed aspects andexamples. For purposes of clarity, not every component may be labeled inevery figure.

FIG. 1 depicts a wearable, ambulatory, external medical device inaccordance with at least one example disclosed herein.

FIG. 2 depicts an arrangement of components of a medical devicecontroller in accordance with at least one example disclosed herein.

FIG. 3 depicts a sensing electrode in accordance with at least oneexample disclosed herein.

FIG. 4 depicts a multi-function electrode in accordance with at leastone example disclosed herein.

FIG. 5 depicts a therapy pad in accordance with at least one exampledisclosed herein.

FIG. 6A depicts a monitoring and treatment process including arrhythmiaverification in accordance with at least one example disclosed herein.

FIG. 6B depicts a monitoring and treatment protocol including an alarmsequence in accordance with at least one example disclosed herein.

FIG. 7 depicts a configurable voting process in accordance with at leastone example disclosed herein.

FIG. 8 depicts an abnormality detection process in accordance with atleast one example disclosed herein.

FIG. 9 depicts an arrhythmia verification process in accordance with atleast one example disclosed herein.

FIG. 10 depicts another wearable, ambulatory, external medical device inaccordance with at least one example disclosed herein.

FIG. 11 depicts another monitoring and treatment process includingarrhythmia verification in accordance with at least one exampledisclosed herein.

FIG. 12 depicts another wearable, ambulatory, external medical device inaccordance with at least one example disclosed herein.

FIG. 13 depicts another monitoring and treatment process includingarrhythmia verification in accordance with at least one exampledisclosed herein.

FIG. 14 depicts another wearable, ambulatory, external medical device inaccordance with at least one example disclosed herein.

FIG. 15 depicts another monitoring and treatment process includingarrhythmia verification in accordance with at least one exampledisclosed herein.

FIG. 16 depicts another wearable, ambulatory, external medical device inaccordance with at least one example disclosed herein.

FIG. 17 depicts another monitoring and treatment process includingarrhythmia verification in accordance with at least one exampledisclosed herein.

FIG. 18 depicts another wearable, ambulatory, external medical device inaccordance with at least one example disclosed herein.

FIG. 19 depicts another monitoring and treatment process includingarrhythmia verification in accordance with at least one exampledisclosed herein.

DETAILED DESCRIPTION Overview

The present disclosure is directed to verification of a cardiacarrhythmia condition, such as tachycardia or fibrillation, prior toadministering one or more electrical therapeutic stimulation pulses to apatient using an ambulatory medical device.

Some ambulatory medical devices can identify a cardiac abnormality(e.g., a cardiac arrhythmia) and deliver one or more therapeuticelectrical pulses to correct the detected abnormality. These devicesrepresent a significant diagnostic and therapeutic advance. With theseambulatory medical devices, the cardiac function of a patient may becontinuously monitored and therapeutic stimulation pulses administeredeven while providing some freedom of movement to the patient.

Despite these significant advantages, conventional ambulatory medicaldevices may occasionally improperly administer a therapeutic stimulationpulse as a result of detecting an abnormality that is not an arrhythmiacondition. To prevent these improperly administered therapeuticstimulation pulses, examples described herein include ambulatory medicaldevices having processes, mechanisms, and systems for verifying aninitial declaration of an arrhythmia condition prior to administering atherapeutic stimulation pulse.

For instance, to verify an initial arrhythmia declaration, some exampleambulatory medical devices described herein include a plurality ofsensing electrode pairs. This plurality of sensing electrode pairs mayinclude a first electrode pair and a second electrode pair distinct fromthe first electrode pair. The first electrode pair may detect firstelectrocardiogram (ECG) signals, and the second electrode pair maydetect second ECG signals. In some examples, the ambulatory medicaldevices are configured to execute one or more abnormality detection andarrhythmia verification processes using these distinct electrode pairsand ECG signals. These one or more abnormality detection and arrhythmiaverification processes may initially determine whether an arrhythmiacondition is present and later verify the arrhythmia condition remainspresent prior to administering a therapeutic stimulation pulse.

More specifically, in some examples, the ambulatory medical device isconfigured to execute an abnormality detection process using the firstelectrode pair. During the abnormality detection process, the ambulatorymedical device acquires and processes first ECG signals detected by thefirst electrode pair. Processing the acquired first ECG signalsgenerates associated first ECG data, which may be analyzed to detect anabnormality (e.g., an arrhythmia condition). Where the analyzed firstECG data indicates an arrhythmia condition, the ambulatory medicaldevice initially declares the presentation of an arrhythmia condition(e.g., stores one or more bits of a specific value at a specific memorylocation) and initiates a treatment process. This treatment process mayinclude a variety of actions.

For instance, in one example of the treatment process, the ambulatorymedical device first issues an alarm to indicate that the ambulatorymedical device has detected an abnormality and declared an arrhythmiacondition. The alarm may include auditory, tactile, and/or visualcomponents. The alarm may further indicate that the patient must respondto the alarm within a predetermined time frame (e.g., 60 seconds) if thepatient wishes to avoid treatment. If the patient responds as indicated(e.g., by pushing a specific response button provided by the ambulatorymedical device within the predetermine time frame), the ambulatorymedical device delays or aborts treatment. However, in some examples, ifthe patient fails to respond within the predetermined time frame, theambulatory medical device continues execution of the treatment protocol.

In some examples, the next step of the treatment protocol is deploymentof conductive gel between the skin of the patient and one or more pairsof electrodes (e.g., sensing and/or treatment electrode pairs). Thisstep is executed to decrease the impedance between the electrode pairsand the patient's skin. In some examples, the conductive gel is deployedbetween one or more pairs of treatment electrodes and the patient'sskin. In some examples, the conductive gel is deployed between one ormore pairs of sensing electrodes (e.g., the second electrode pair) andthe patient's skin. In some examples, the conductive gel is deployedbetween one or more pairs of treatment electrodes and the patient's skinand between one or more pairs of sensing electrodes and the patient'sskin. In some examples, the conductive gel is deployed between one ormore pairs of multi-function electrodes (e.g., electrodes configured tofunction as both treatment and sensing electrodes) and the patient'sskin. Other types of electrodes may be involved within the geldeployment process, and the examples disclosed herein are not limited toparticular types of electrode pairs. After completion of (or during) geldeployment, the treatment protocol may continue with additional alarmsthat instruct bystanders not to touch the patient.

In some examples of the treatment protocol, the ambulatory medicaldevice next charges its capacitors and, optionally, issues another alarmto clearly warn of an imminent delivery of a therapeutic stimulationpulse. According to some examples, the treatment protocol culminateswith the delivery of the therapeutic stimulation pulse to the patient'sskin via a pair of treatment electrodes and the conductive gel. Afterthe treatment protocol is complete, the ambulatory medical devicereturns to execution of the abnormality detection process.

In some examples, the ambulatory medical device implements (e.g., duringexecution of the treatment protocol) an arrhythmia verification processusing the second electrode pair. During execution of the arrhythmiaverification process, the ambulatory medical device acquires andprocesses second ECG signals detected by the second electrode pair.Processing the acquired second ECG signals generates associated secondECG data, which may be analyzed to verify the arrhythmia condition.Where the ambulatory medical device is able to verify the initialarrhythmia declaration using the analyzed second ECG data, theambulatory medical device continues the treatment protocol. However,where the ambulatory medical device is unable to verify the initialarrhythmia declaration using the analyzed second ECG data, theambulatory medical device suspends the treatment protocol and returns toexecution of the abnormality detection process.

In examples, the second ECG signals have a higher reliability and aretherefore more likely to accurately indicate the actual occurrence of anarrhythmia condition. In an example, the higher reliability of thesecond ECG signals relative to the first ECG signals can be accomplishedby, for example, using a different type of sensor for the secondelectrode pair compared to the first electrode pair. While the firstelectrode pair can use a dry ECG electrode sensing mechanism, the secondelectrode pair can use a different mechanism (e.g., a wet, gel basedconductive sensing mechanism). In some examples, a sensing mechanism forthe second electrode pair is selected to be more accurate than thesensing mechanism for the first electrode pair. Regardless of thesensing mechanism, accuracy of the first electrode pair and the secondelectrode pair may be optionally improved by administering a conductivegel between skin of the patient and the second electrode pair to improvequality of the sensed ECG signals. In examples, the higher reliabilityof the second ECG signals relative to the first ECG signals can beaccomplished by, for example, applying different analyses to the secondECG data, such as those that increase a statistical confidence level ofa conclusion drawn from the analyzed second ECG data. These analyses mayuse stricter criteria for identifying an arrhythmia condition, mayprocess longer samples of the second ECG data than the samples of firstECG data previously processed, may process more samples of the secondECG data than the samples of the first ECG data previously processed,and/or may process an overall amount of second ECG data that is greaterthan the amount of first ECG data previously processed. Details of suchadditional analyses are provided below. In examples, the physicalconditions under which the second ECG signals are obtained (e.g., thatimprove electrical contact between the patient and the second electrodepair) are improved so as to improve reliability compared to the firstECG signals.

An advantage of examples described herein includes improved patientcomfort and health by reducing unnecessary treatment based on falsepositive detections of arrhythmia conditions. Another advantage ofexamples described herein includes improved ambulatory medical deviceperformance by reducing the number of times an unnecessary therapeuticstimulation pulse is administered to a patient, which then reduces thefrequency with which electrical storage systems in the ambulatorymedical device are recharged and other components are refurbished (e.g.,replenishment of conductive gel reservoirs, replacement of therapyelectrodes, etc.).

Example Medical Devices

The teachings of the present disclosure can be generally applied toexternal medical monitoring and/or treatment devices (e.g., devices thatare not completely implanted within the patient's body). Externalmedical devices can include, for example, ambulatory medical devicesthat are capable of and designed for moving with the patient as thepatient goes about his or her daily routine. An example ambulatorymedical device can be a wearable medical device such as a wearablecardioverter defibrillator (WCD), a wearable cardiac monitoring device,an in-hospital device such as an in-hospital wearable defibrillator, ashort-term wearable cardiac monitoring and/or therapeutic device, mobiletelemetry devices, and other similar wearable medical devices.

The wearable medical device is capable of continuous use by the patient.For example, the wearable medical device can be configured to be worn bya patient for as many as 24 hours a day. In some implementations, thecontinuous use may be substantially or nearly continuous in nature. Thatis, the wearable medical device may be continuously used, except forsporadic periods during which the use temporarily ceases (e.g., whilethe patient bathes, while the patient is refit with a new and/or adifferent garment, while the battery is charged/changed, while thegarment is laundered, etc.). Such substantially or nearly continuous useas described herein may nonetheless qualify as continuous use. Oneillustration of a sporadic period in which use of the wearable medicaldevice temporarily and briefly ceases is when the patient removes thewearable medical device for a short portion of the day (e.g., for halfan hour) to bathe.

Further, the wearable medical device can be configured as a long term orextended use medical device. Such devices can be configured to be usedby the patient for an extended period of several days, weeks, months, oreven years. In some examples, the wearable medical device can be used bya patient for an extended period of at least one week. In some examples,the wearable medical device can be used by a patient for an extendedperiod of at least 30 days. In some examples, the wearable medicaldevice can be used by a patient for an extended period of at least onemonth. In some examples, the wearable medical device can be used by apatient for an extended period of at least two months. In some examples,the wearable medical device can be used by a patient for an extendedperiod of at least three months. In some examples, the wearable medicaldevice can be used by a patient for an extended period of at least sixmonths. In some examples, the wearable medical device can be used by apatient for an extended period of at least one year. In someimplementations, the extended use can be uninterrupted until a physicianor other caregiver provide specific instruction to the patient to stopuse of the wearable medical device.

Regardless of the extended period of wear, the use of the wearablemedical device can include continuous or nearly continuous wear by thepatient as described above. For example, the continuous use can includecontinuous wear or attachment of the wearable medical device to thepatient, e.g., through one or more of the electrodes as describedherein, during both periods of monitoring and periods when the devicemay not be monitoring the patient but is otherwise still worn by orotherwise attached to the patient. The wearable medical device can beconfigured to continuously monitor the patient for cardiac-relatedinformation (e.g., ECG information, including arrhythmia information,heart sounds, etc.) and/or non-cardiac information (e.g., blood oxygen,the patient's temperature, glucose levels, tissue fluid levels, and/orlung sounds). The wearable medical device can carry out its monitoringin periodic or aperiodic time intervals or times. For example, themonitoring during intervals or times can be triggered by a user actionor another event.

As noted above, the wearable medical device can be configured to monitorother physiologic parameters of the patient in addition to cardiacrelated parameters. For example, the wearable medical device can beconfigured to monitor, for example, lung sounds (e.g., using microphonesand/or accelerometers), heart sounds, breath sounds, sleep relatedparameters (e.g., snoring, sleep apnea), tissue fluids (e.g., usingradio-frequency transmitters and sensors), among others.

Other example wearable medical devices include automated cardiacmonitors and/or defibrillators for use in certain specialized conditionsand/or environments such as in combat zones or within emergencyvehicles. Such devices can be configured so that they can be usedimmediately (or substantially immediately) in a life-saving emergency.In some examples, the wearable medical devices described herein can bepacing-enabled, e.g., capable of providing therapeutic pacing pulses tothe patient.

In implementations, an example therapeutic medical device can include anin-hospital continuous monitoring defibrillator and/or pacing device,for example, an in-hospital wearable defibrillator. In such an example,the electrodes can be configured to couple externally to a skin of apatient, such as by attaching the electrode to the patient's skin. Forexample, the electrodes can include disposable adhesive electrodes. Forexample, the electrodes can include sensing and therapy componentsdisposed on separate sensing and therapy electrode adhesive patches. Insome implementations, both sensing and therapy components can beintegrated and disposed on a same electrode adhesive patch that is thenattached to the patient (also referred to herein as a “multi-function”electrode). In an example implementation, the electrodes can include afront adhesively attachable therapy electrode, a back adhesivelyattachable therapy electrode, and a plurality of adhesively attachablesensing electrodes. For example, the front adhesively attachable therapyelectrode attaches to the external surface of the skin of the patient onthe front of the patient's torso to deliver pacing or defibrillatingtherapy. Similarly, the back adhesively attachable therapy electrodeattaches to the external surface of the skin of the patient on the backof the patient's torso. In an example scenario, at least three ECGadhesively attachable sensing electrodes can be attached to at leastabove the patient's chest near the right arm, above the patient's chestnear the left arm, and towards the bottom of the patient's chest in amanner prescribed by a trained professional.

A patient being monitored by an in-hospital defibrillator and/or pacingdevice may be confined to a hospital bed or room for a significantamount of time (e.g., 90% or more of the patient's stay in thehospital). As a result, a user interface can be configured to interactwith a user other than the patient, e.g., a nurse, for device-relatedfunctions such as initial device baselining, setting and adjustingpatient parameters, and changing the device batteries.

In implementations, an example of a therapeutic medical device caninclude a short-term continuous monitoring defibrillator and/or pacingdevice, for example, a short-term outpatient wearable defibrillator. Forexample, such a short-term outpatient wearable defibrillator can beprescribed by a physician for patients presenting with syncope. Awearable defibrillator can be configured to monitor patients presentingwith syncope by, e.g., analyzing the patient's cardiac activity foraberrant patterns that can indicate abnormal physiological function. Forexample, such aberrant patterns can occur prior to, during, or after theonset of symptoms. In such an example implementation of the short-termwearable defibrillator, the electrode assembly can be adhesivelyattached to the patient's skin and have a similar configuration as thein-hospital defibrillator described above.

In some implementations, the medical device may be a patient monitoringdevice with separable treatment or therapy functions. For example, sucha patient monitoring device can include a cardiac monitoring device or acardiac monitor that is configured to monitor one or more cardiacphysiological parameters of a patient, e.g., for remotely monitoringand/or diagnosing a condition of the patient. The treatment or therapyfunctions may be contained in a separate module that may be coupled ordecoupled as appropriate for individual patients. For example, cardiacphysiological parameters monitored by such a device may include apatient's electrocardiogram (ECG) information, heart sounds (e.g., usingaccelerometers or microphones), and other related cardiac information.The patient may carry such a cardiac monitoring device with separabletreatment or therapy functions as the patient goes about a dailyroutine. For example, in the usual course of wear such a device mayinclude the cardiac monitor portion (without treatment or therapyfunctions) and may be configured to detect the patient's ECG through aplurality of cardiac sensing electrodes. The cardiac monitor may beattached to a patient via a plurality of (e.g., two or more) adhesivecardiac sensing electrodes disposed about the patient's torso. Suchcardiac monitors are used in remote mobile cardiac monitoringapplications, such as continuous cardiac event monitoring. For example,such monitors may be used in patient populations reporting irregularcardiac symptoms and/or conditions. Example cardiac conditions caninclude atrial fibrillation, bradycardia, tachycardia, atrio-ventricularblock, Lown-Ganong-Levine syndrome, atrial flutter, sino-atrial nodedysfunction, cerebral ischemia, syncope, atrial pause, and/or heartpalpitations. For example, such patients may be prescribed a cardiacmonitor for an extended period of time, e.g., 10 to 30 days, or more. Insome mobile cardiac telemetry applications, a portable cardiac monitorcan be configured to substantially continuously monitor the patient fora cardiac anomaly, and when such an anomaly is detected, the monitor mayautomatically send data relating to the anomaly to a remote server. Theremote server may be located within a 24-hour manned monitoring center,where the data is interpreted by qualified, cardiac-trained reviewersand/or caregivers, and feedback provided to the patient and/or adesignated caregiver via detailed periodic or event-triggered reports.In certain cardiac event monitoring applications, the cardiac monitor isconfigured to allow the patient to manually press a response button onthe cardiac monitor to report a symptom. For example, a patient mayreport symptoms such as a skipped beat, shortness of breath, lightheadedness, racing heart rate, fatigue, fainting, chest discomfort,weakness, dizziness, and/or giddiness. The cardiac monitor can recordpredetermined physiologic parameters of the patient (e.g., ECGinformation) for a predetermined amount of time (e.g., 1-30 minutesbefore and 1-30 minutes after a reported symptom). The cardiac monitorcan be configured to monitor physiologic parameters of the patient otherthan cardiac related parameters. For example, the cardiac monitor can beconfigured to monitor, for example, heart sounds (e.g., usingaccelerometers or microphones), lung sounds, breath sounds, sleeprelated parameters (e.g., snoring, sleep apnea), tissue fluids, amongothers. If a treatment and/or therapeutic function is deemed necessary,such as when the cardiac monitor indicates that the patient is at anincreased risk of a treatable arrhythmia, the patient may be directed toattach a treatment module containing the therapy delivery circuit 202and associated therapy electrodes 220 (FIG. 2). Examples of suchtreatable arrhythmias can include paceable conditions such asbradycardia, tachycardia, and other irregular rhythm conditions, orconditions that require a defibrillation shock such as VT or VF.

FIG. 1 illustrates an example medical device 100 that is external,ambulatory, and wearable by a patient 102, and configured to implementone or more configurations described herein. For example, the medicaldevice 100 can be a non-invasive medical device configured to detect anarrhythmia condition using at least one first sensing electrode, verifywhether the initial detected arrhythmia is correct or refute the initialdeclaration, and either provide a therapeutic stimulation pulse to theheart of the patient or return to a monitoring mode, respectivelydepending on the result of the verification. Such a medical device 100can be, for example, an ambulatory medical device that is capable of,and designed for, moving with the patient as the patient goes about hisor her daily routine. For example, the medical device 100, such as theLifeVest® wearable cardioverter defibrillator available from ZOLL®Medical Corporation, as described herein can be bodily-attached to thepatient. Such wearable defibrillators typically are worn nearlycontinuously or substantially continuously for two to three months at atime. During the period of time in which they are worn by the patient,the wearable defibrillator can be configured to continuously orsubstantially continuously monitor the vital signs of the patient and,upon determination that treatment is required, can be configured todeliver one or more therapeutic stimulation pulses to the patient. Forexample, such therapeutic stimulation pulses (also referred to aselectrical signals or shocks) can be pacing, defibrillation, ortranscutaneous electrical nerve stimulation (TENS) pulses.

The medical device 100 can include one or more of the following: agarment 110, one or more sensing electrode pairs 112 (e.g.,anterior/posterior electrodes 112 a and side/side electrodes 112 b), oneor more therapy electrodes pairs 114 (e.g., anterior therapy electrode114 a and posterior electrodes 114 b), a medical device controller 120,a connection pod 130, a patient interface pod 140, a belt 150, or anycombination of these. In some examples, at least some of the componentsof the medical device 100 can be configured to be affixed to the garment110 (or in some examples, permanently integrated into the garment 110),which can be worn about the patient's torso.

The medical device controller 120 can be operatively coupled to thesensing electrodes 112, which in turn can be affixed to the garment 110(e.g., assembled into the garment 110 or removably attached to thegarment using, for example, hook and loop fasteners). In someimplementations, the sensing electrodes 112 can be permanentlyintegrated into the garment 110. The medical device controller 120 canbe operatively coupled to a pair of therapy electrodes 114. For example,the therapy electrodes 114 can also be assembled into the garment 110,or, in some implementations, the therapy electrodes 114 can bepermanently integrated into the garment 110.

Component configurations other than those shown in FIG. 1 are possible.For example, the sensing electrodes 112 can be configured to be attachedat various positions about the body of the patient 102. The sensingelectrodes 112 can be operatively coupled to the medical devicecontroller 120 through the connection pod 130. In some implementations,the sensing electrodes 112 can be adhesively attached to the patient102. In some implementations, the sensing electrodes 112 and therapyelectrodes 114 can be included on a single integrated patch andadhesively applied to the patient's body.

The sensing electrodes 112 can be configured to detect one or morecardiac signals. Examples of such signals include ECG signals, heartsounds, and/or other sensed cardiac physiological signals from thepatient. The sensing electrodes 112 can also be configured to detectother types of patient physiological parameters, such as tissue fluidlevels, lung sounds, respiration movement and/or sounds, patientmovement, etc. Example sensing electrodes 112 include dry electrodeswith an oxide coating such as tantalum pentoxide electrodes, asdescribed in, for example, U.S. Pat. No. 6,253,099 titled “CardiacMonitoring Electrode Apparatus and Method,” which is hereby incorporateherein by reference in its entirety.

Example sensing electrodes 112 also include conductive electrodes with afoundational layer (e.g., made of foam), an electrically conductiveelement (e.g., made of tin, silver-silver chloride, etc.), and anelectrolytic layer (e.g., made of hydrogel) that electrically couplesthe conductive element to the patient's skin. In some examples, thetherapy electrodes 114 can also be configured to include sensorsconfigured to detect ECG signals as well as other physiological signalsof the patient. In an example, one or more of the sensing electrodes 112and the therapy electrodes 114 are comprised within an electrodeassembly. In an example, an electrode assembly includes a plurality ofelectrodes and a corresponding plurality of electrical conductors formedon a dielectric film. Each respective electrode includes a conductiveelement that defines a contact area of the respective electrode. Theconductive elements may be formed by depositing a conductive material onthe dielectric film. The electrical conductors may be formed integrallywith the conductive elements on the dielectric film or they may beformed separately and electrically connected to the conductive elements.The electrical conductors may be covered with an insulating layer toelectrically isolate them from an upper surface of the adhesive filmlayer and the subject's skin. Moreover, details regarding theconstruction of an ECG electrode that may be included in the electrodeassembly can be found in U.S. Patent Application Publication No.2013/0325096 titled “Long Term Wear Multifunction Biomedical Electrode,”which is hereby incorporated herein by reference in its entirety.

In some examples, the electrode assembly and/or the electrodes itcomprises are included within a sensor assembly. Such a sensor assemblymay include other, non-ECG sensors described herein, such as the heartsounds sensors 224 and/or the tissue fluid sensors 226 described belowwith reference to FIG. 2. In certain examples, the sensor assembly alsoincludes non-ECG sensors such as a pulse oximeter that measures arterialoxygen saturation via a plethysmograph sensor, such as aphotoplethysmograph (PPG) sensor.

In examples, a therapy electrode 114 can be constructed to include atleast one conductive gel dispenser that, upon instruction by geldispenser circuitry and a processor, applies conductive gel so that itis disposed between a skin of the patient and a therapy electrode. Whilethe term “therapy electrode” is used herein, it will be understood thatthis term may be equivalently substituted with “therapy pad” whenapplication of conductive gel is also described.

The connection pod 130 can, in some examples, include a signal processorconfigured to amplify, filter, and digitize cardiac signals sensed bythe sensing electrodes 112 prior to transmitting the cardiac signals tothe medical device controller 120. One or more therapy electrodes 114can be configured to deliver one or more therapeutic defibrillatingshocks to the body of the patient 102 when the medical device 100determines that such treatment is warranted based on the signalsdetected by the sensing electrodes 112 and processed by the medicaldevice controller 120. Example therapy electrodes 114 can includeconductive metal electrodes such as stainless-steel electrodes thatinclude, in certain implementations, one or more conductive geldeployment devices configured to deliver conductive gel to the metalelectrode prior to delivery of a therapeutic shock.

In some implementations, medical devices as described herein can beconfigured to switch between a therapeutic medical device and amonitoring medical device that is configured to only monitor a patient(e.g., not provide or perform any therapeutic functions). For example,therapeutic components such as the therapy electrodes 114 and associatedcircuitry can be optionally decoupled from (or coupled to) or switchedout of (or switched in to) the medical device. For example, a medicaldevice can have optional therapeutic elements (e.g., defibrillationand/or pacing electrodes, components, and associated circuitry) that areconfigured to operate in a therapeutic mode. The optional therapeuticelements can be physically decoupled from the medical device to convertthe therapeutic medical device into a monitoring medical device for aspecific use (e.g., for operating in a monitoring-only mode) or apatient. Alternatively, the optional therapeutic elements can bedeactivated (e.g., by means or a physical or a software switch),essentially rendering the therapeutic medical device as a monitoringmedical device for a specific physiologic purpose or a particularpatient. As an example of a software switch, an authorized person canaccess a protected user interface of the medical device and select apreconfigured option or perform some other user action via the userinterface to deactivate the therapeutic elements of the medical device100.

Example Medical Device Controller

FIG. 2 illustrates a sample component-level view of the medical devicecontroller 120 as initially shown in FIG. 1. As shown in FIG. 2, themedical device controller 120 can include a therapy delivery circuit202, a data storage 204, a network interface 206, a user interface 208,at least one battery 210, a sensor interface 212, cardiac monitor 214, atreatment controller 216, and least one processor 218.

The therapy delivery circuit 202 can be coupled to one or moreelectrodes 220 configured to provide therapy to the patient (e.g.,therapy electrodes 114 a-b as described above in connection with FIG.1). For example, the therapy delivery circuit 202 can include, or beoperably connected to, circuitry components that are configured togenerate and provide the therapeutic electrical pulse or shock. Thecircuitry components can include, for example, resistors, capacitors,relays and/or switches, electrical bridges such as an h-bridge (e.g.,including a plurality of insulated gate bipolar transistors or IGBTs),voltage and/or current measuring components, and other similar circuitrycomponents arranged and connected such that the circuitry componentswork in concert with the therapy delivery circuit and under control ofone or more processors (e.g., processor 218) to provide, for example,one or more pacing or defibrillation therapeutic stimulation pulses.

Pacing pulses can be used to treat cardiac arrhythmias such asbradycardia (e.g., less than 30 beats per minute) and tachycardia (e.g.,more than 150 beats per minute) using, for example, fixed rate pacing,demand pacing, anti-tachycardia pacing, and the like. Defibrillationpulses can be used to treat ventricular tachycardia and/or ventricularfibrillation.

The capacitors can include a parallel-connected capacitor bankconsisting of a plurality of capacitors (e.g., two, three, four or morecapacitors). These capacitors can be switched into a series connectionduring discharge for a defibrillation pulse. For example, fourcapacitors of approximately 650 uF can be used. The capacitors can havebetween a 350 to 500 volt surge rating and can be charged inapproximately 15 to 30 seconds from a battery pack,_such as the at leastone battery 210.

For example, each defibrillation pulse can deliver between 60 to 180joules of energy. In some implementations, the defibrillating pulse canbe a biphasic truncated exponential waveform, whereby the pulse canswitch between a positive and a negative portion (e.g., chargedirections). This type of waveform can be effective at defibrillatingpatients at lower energy levels when compared to other types oftherapeutic stimulation pulses (e.g., such as monophasic pulses). Forexample, an amplitude and a width of the two phases of the energywaveform can be automatically adjusted to deliver a precise energyamount (e.g., 150 joules) regardless of the patient's body impedance.The therapy delivery circuit 202 can be configured to perform theswitching and pulse delivery operations, e.g., under control of theprocessor 218. As the energy is delivered to the patient, the amount ofenergy being delivered can be tracked. For example, the amount of energycan be kept to a predetermined constant value even as the pulse waveformis dynamically controlled based on factors such as the patient's bodyimpedance which the pulse is being delivered.

The data storage 204 can include one or more of non-transitory computerreadable media, such as flash memory, solid state memory, magneticmemory, optical memory, cache memory, combinations thereof, and others.The data storage 204 can be configured to store executable instructionsand data used for operation of the medical device controller 120. Incertain implementations, the data storage can include executableinstructions that, when executed, are configured to cause the processor218 to perform one or more functions.

In some examples, the network interface 206 can facilitate thecommunication of information between the medical device controller 120and one or more other devices or entities over a communications network.For example, where the medical device controller 120 is included in anambulatory medical device (such as medical device 100), the networkinterface 206 can be configured to communicate with a remote computingdevice such as a remote server or other similar computing device.

In certain implementations, the user interface 208 can include one ormore physical interface devices such as input devices, output devices,and combination input/output devices and a software stack configured todrive operation of the devices. These user interface elements may rendervisual, audio, and/or tactile content, including content relating tolocation-specific processing. Thus, the user interface 208 may receiveinput or provide output, thereby enabling a user to interact with themedical device controller 120.

The medical device controller 120 can also include at least one battery210 configured to provide power to one or more components integrated inthe medical device controller 120. The battery 210 can include arechargeable multi-cell battery pack. In one example implementation, thebattery 210 can include three or more 2200 mAh lithium ion cells thatprovide electrical power to the other device components within themedical device controller 120. For example, the battery 210 can provideits power output in a range of between 20 mA to 1000 mA (e.g., 40 mA)output and can support 24 hours, 48 hours, 72 hours, or more, of runtimebetween charges. In certain implementations, the battery capacity,runtime, and type (e.g., lithium ion, nickel-cadmium, or nickel-metalhydride) can be changed to best fit the specific application of themedical device controller 120.

The sensor interface 212 can be coupled to one or more sensorsconfigured to monitor one or more physiological parameters of thepatient. As shown, the sensors may be coupled to the medical devicecontroller 120 via a wired or wireless connection. The sensors caninclude one or more electrocardiogram (ECG) electrodes 222 (e.g.,similar to sensing electrodes 112 as described above in connection withFIG. 1), heart sounds sensors 224, and tissue fluid monitors 226 (e.g.,based on ultra-wide band radiofrequency devices). As such, the sensorinterface 212 may include amplifiers and analog to digital converters tocondition and digitize signals acquired by the sensors.

The ECG electrodes 222 can monitor a patient's ECG information. Forexample, the ECG electrodes 222 can be galvanic, conductive and/or dryelectrodes configured to measure changes in a patient'selectrophysiology to measure the patient's ECG information. The ECGelectrodes 222 can transmit information descriptive of the ECG signalsto the sensor interface 212 for subsequent analysis.

The heart sounds sensors 224 can detect a patient's heart soundinformation. For example, the heart sounds sensors 224 can be configuredto detect heart sound values including any one or all of S1, S2, S3, andS4. From these heart sound values, certain heart sound metrics may becalculated, including any one or more of electromechanical activationtime (EMAT), percentage of EMAT (% EMAT), systolic dysfunction index(SDI), and left ventricular systolic time (LVST). The heart soundssensors 224 can include an acoustic sensor configured to detect soundsfrom a subject's cardiac system and provide an output signal responsiveto the detected heart sounds. The heart sounds sensors 224 can alsoinclude a multi-channel accelerometer, for example, a three-channelaccelerometer configured to sense movement in each of three orthogonalaxes such that patient movement/body position can be detected andcorrelated to detected heart sounds information. The heart soundssensors 224 can transmit information descriptive of the heart soundsinformation to the sensor interface 212 for subsequent analysis.

The tissue fluid monitors 226 can use radio frequency (RF) basedtechniques to assess fluid levels and accumulation in a patient's bodytissue. For example, the tissue fluid monitors 226 can be configured tomeasure fluid content in the lungs, typically for diagnosis andfollow-up of pulmonary edema or lung congestion in heart failurepatients. The tissue fluid monitors 226 can include one or more antennasconfigured to direct RF waves through a patient's tissue and measureoutput RF signals in response to the waves that have passed through thetissue. In certain implementations, the output RF signals includeparameters indicative of a fluid level in the patient's tissue. Thetissue fluid monitors 226 can transmit information descriptive of thetissue fluid levels to the sensor interface 212 for subsequent analysis.

The sensor interface 212 can be coupled to any one or combination ofsensing electrodes/other sensors to receive other patient dataindicative of patient parameters. Once data from the sensors has beenreceived by the sensor interface 212, the data can be directed by theprocessor 218 to an appropriate component within the medical devicecontroller 120. For example, if heart data is collected by heart soundssensor 224 and transmitted to the sensor interface 212, the sensorinterface 212 can transmit the data to the processor 218 which, in turn,relays the data to the cardiac monitor 214 and/or the treatmentcontroller 216. These data can also be stored on the data storage 204.

According to some examples illustrated by FIG. 2, the cardiac monitor214 is configured to initiate and control monitoring of a patient'scardiac function and coordinate identification of arrhythmiasexperienced by the patient. When instructing mechanisms that performthese functions, in some examples the cardiac monitor 214 detectsarrhythmias by analyzing ECG data received from the sensor interface 212for patterns (e.g. heart rates) indicative of arrhythmias. Responsive toidentifying a data pattern indicative of an arrhythmia, the cardiacmonitor 214 initiates action by the treatment controller 216. In someexamples, the cardiac monitor 214 analyzes additional, non-ECG datareceived from the sensor interface 212 to ascertain the patient'sphysical condition. For instance, the cardiac monitor 214 may analyzePPG data to determine oxygen saturation of the patient's blood. Thecardiac monitor 214 may also analyze accelerometer data to determinepatient movement and/or heart sounds. Patient movement may, in turn,indicate a general lack of body movement and/or respiration.

According to some examples illustrated by FIG. 2, the treatmentcontroller 216 is configured to initiate and control treatment of anarrhythmia identified by the cardiac monitor 214. When executingaccording to this configuration, in some examples, the treatmentcontroller 216 executes a treatment protocol specific to the particularidentified arrhythmia. For instance, the treatment controller 216 maypace a patient experiencing bradycardia or ventricular tachycardia ormay defibrillate a patient experiencing atrial or ventricularfibrillation. In some examples, the treatment controller 216 initiatesdeployment of electrically conductive gel as part of the treatmentprotocol. Also, in some examples, the treatment controller 216 monitorsthe reaction of the patient's heart to the treatment protocol and takesfurther action based on the reaction of the patient's heart. Thisfurther action may include altering the treatment protocol and/orescalating notifications to external parties.

Both the cardiac monitor 214 and the treatment controller 216 can beimplemented using hardware or a combination of hardware and software.For instance, in some examples, the cardiac monitor 214 and/or thetreatment controller 216 are implemented as software components that arestored within the data storage 204 and executed by the processor 218. Inthis example, the instructions included in the cardiac monitor 214and/or the treatment controller 216 can cause the processor 218 tomonitor for, detect, and treat arrhythmias. In other examples, thecardiac monitor 214 and/or the treatment controller 216 areapplication-specific integrated circuits (ASICs) that are coupled to theprocessor 218 and configured to monitor for, detect, and treatarrhythmias. Thus, in examples the cardiac monitor 214 and the treatmentcontroller 216 are not limited to a particular hardware or softwareimplementation.

In some implementations, the processor 218 includes one or moreprocessors (or one or more processor cores) that each are configured toperform a series of instructions that result in manipulated data and/orcontrol the operation of the other components of the medical devicecontroller 120. In some implementations, when executing a specificprocess (e.g., cardiac monitoring, treatment, etc.), the processor 218can be configured to make specific logic-based determinations based oninput data received, and be further configured to provide one or moreoutputs that can be used to control or otherwise inform subsequentprocessing to be carried out by the processor 218 and/or otherprocessors or circuitry with which processor 218 is communicativelycoupled. Thus, the processor 218 reacts to specific input stimulus in aspecific way and generates a corresponding output based on that inputstimulus. In some example cases, the processor 218 can proceed through asequence of logical transitions in which various internal registerstates and/or other bit cell states internal or external to theprocessor 218 may be set to logic high or logic low. As referred toherein, the processor 218 can be configured to execute a function wheresoftware is stored in a data store coupled to the processor 218, thesoftware being configured to cause the processor 218 to proceed througha sequence of various logic decisions that result in the function beingexecuted. The various components that are described herein as beingexecutable by the processor 218 can be implemented in various forms ofspecialized hardware, software, or a combination thereof. For example,the processor can be a digital signal processor (DSP) such as a 24-bitDSP processor. The processor can be a multi-core processor, e.g., havingtwo or more processing cores. The processor can be an Advanced RISCMachine (ARM) processor such as a 32-bit ARM processor. The processorcan execute an embedded operating system, and include services providedby the operating system that can be used for file system manipulation,display & audio generation, basic networking, firewalling, dataencryption and communications.

Example Arrhythmia Verification Systems, Devices, and Processes

As described above, some examples disclosed herein include an ambulatorymedical device (e.g., the medical device 100) configured to monitor apatient for cardiac abnormalities, detect and declare arrhythmiaconditions, and verify arrhythmia declarations prior to treating thepatient with one or more therapeutic pulses. This verification improvespatient comfort, for example by avoiding needless therapeuticintervention. In some examples, the at least one processor executes anabnormality detection process when analyzing first ECG data based onfirst ECG signals and executes an arrhythmia verification process toanalyze second ECG data based on second ECG signals.

To detect an abnormality, declare an arrhythmia condition, and verify anarrhythmia declaration, some example ambulatory medical devicesdescribed herein statically and/or dynamically associate electrodes intoa plurality of electrode pairs. This plurality of electrode pairs mayinclude a first electrode pair and a second electrode pair distinct fromthe first electrode pair. The first electrode pair detects first ECGsignals, and the second electrode pair detects second ECG signals. Insome examples, the ambulatory medical devices are configured to executeone or more abnormality detection and arrhythmia verification processesusing these distinct electrode pairs and ECG signals. These processesmay initially determine whether an arrhythmia condition is present andlater verify the arrhythmia condition remains present prior toadministering a therapeutic stimulation pulse.

More specifically, in some examples, the ambulatory medical device isconfigured to execute a cardiac abnormality detection process using thefirst electrode pair. During the abnormality detection process, theambulatory medical device acquires and processes first ECG signalsdetected by the first electrode pair. Processing the acquired first ECGsignals generates associated first ECG data, which may be analyzed todetect an abnormality (e.g., an arrhythmia condition). Where theanalyzed first ECG data indicates an arrhythmia condition, theambulatory medical device records an initial declaration of thearrhythmia condition and initiates a treatment protocol. As describedabove, this treatment protocol may include acts such as issuing an alarmto indicate that the ambulatory medical device has detected anarrhythmia condition, deploying conductive gel where no response to thealarm is received, charging capacitors, issuing a final warning tobystanders, and delivering a therapeutic stimulation pulse. After thetreatment protocol is complete, the ambulatory medical device returns toexecution of the abnormality detection process.

In some examples, the ambulatory medical device implements (e.g., duringexecution of the treatment protocol) an arrhythmia verification processusing the second electrode pair. The arrhythmia verification process maybe executed, for example, just prior to delivering the therapeuticstimulation pulse (e.g., after application of the conductive gel betweenthe second electrode pair and the patient's skin). The presence of theconductive gel increases the quality of the electrical connectionbetween the electrodes and the patient's skin. Thus, the presence of thegel may aid the function of a therapy electrode in providing therapeuticstimulation pulses to the patient's heart. Similarly, the presence ofthe gel may aid a sensing electrode in acquiring ECG signals descriptiveof the patient's cardiac activity. During execution of the arrhythmiaverification process, the ambulatory medical device acquires andprocesses second ECG signals detected by the second electrode pair.Processing the acquired second ECG signals generates associated secondECG data, which may be analyzed to verify the arrhythmia condition.Where the ambulatory medical device is able to verify the initialarrhythmia declaration using the analyzed second ECG data, theambulatory medical device continues the treatment protocol. However,where the ambulatory medical device is unable to verify the initialarrhythmia declaration using the analyzed second ECG data, theambulatory medical device suspends the treatment protocol and returns toexecution of the abnormality detection process.

Although some examples focus on the use of ECG data for the abnormalitydetection and arrhythmia verification, other examples use other data inaddition to, or as a replacement of, the ECG data. This other data mayinclude PPG and/or accelerometer data. How these examples utilize thisdata is described further below.

To implement the abnormality detection and arrhythmia verificationprocesses, some examples of the ambulatory medical device include amedical device controller (e.g., the medical device controller 120) andone or more pairs of electrodes. In these examples, the medical devicecontroller may include least one processor (e.g., processor 218) that isin electrical communication with the first and second electrode pairs toacquire the first and second ECG signals. The at least one processor isconfigured to process the first ECG signals to generate first ECG dataand to analyze the first ECG data to detect abnormalities and declarearrhythmia conditions. The at least one processor is also configured toprocess the second ECG signals to generate second ECG data and toanalyze the second ECG data to verify initial declarations of arrhythmiaconditions. The first ECG signals and the second ECG signals may beacquired during distinct and/or overlapping time intervals.

The first and second electrode pairs may include therapy electrodes(e.g., therapy electrodes 114), sensing electrodes (e.g., sensingelectrodes 112), multi-function electrodes (i.e., electrodes thatinclude elements that enable application as both a sensing electrode anda therapy electrode) or some hybrid combination of differing types. Theelectrodes may include conductive ECG electrodes and/or dry ECGelectrodes.

A dry electrode can include a metal substrate with an oxide coatingdeposited on the substrate. For example, such a dry electrode caninclude tantalum-tantalum pentoxide electrodes, as described in, forexample, U.S. Pat. No. 6,253,099 titled “Cardiac Monitoring ElectrodeApparatus and Method,” which is hereby incorporated herein by referencein its entirety. For example, a dry electrode can be constructed byforming a tantalum metal substrate and depositing a tantalum pentoxidelayer on the metal surface. An anodizing process can be used to form theoxide layer. The oxide layer can cover an entire surface of the metalsubstrate including the outer edges. Such a dry electrode can be placeddirectly on a patient's skin to acquire ECG signals without the presenceof an electrolyte. A dry electrode can be regarded as havingcharacteristics close to a polarizable electrode, for example, becauseno actual charge transfers across the electrode interface. In thissense, a dry electrode behaves like a capacitor where it can be regardedas sensing displacement current across the electrode interface ratherthan actual charge transfer across the interface.

Conductive sensing electrodes, on the other hand, include anelectrically conductive element (e.g., made of tin, silver-silverchloride, etc.), and an electrolytic gel (e.g., hydrogel) thatelectrically couples the conductive element to the patient's skin. Forexample, the hydrogel may be combined with an adhesive material tofacilitate close coupling to the patient's skin. In otherimplementations, the gel may be stored in a gel dispenser that isconfigured to deploy when needed as described in detail below (FIG. 3).A conductive electrode can be regarded as having characteristics closeto a nonpolarizable electrode, for example, because the conductiveelectrode senses actual charge transfer or current that passes acrossthe electrode-electrolytic interface based on ionic conduction on thepatient's skin.

In some examples, the ambulatory medical device is configured to executethe abnormality detection process using ECG data based on signalsacquired by dry sensing electrodes and to execute the arrhythmiaverification process using ECG data based on signals acquired byconductive sensing electrodes. Dry sensing electrodes are describedabove with reference to FIGS. 1 and 2. FIG. 3 illustrates a conductivesensing electrode that may be incorporated into some examples. FIG. 4illustrates a conductive multi-function electrode that may beincorporated into some examples. FIG. 5 illustrates a therapy pad andelectrode that may be incorporated into some examples and that may beused as a conductive sensing electrode.

FIG. 3 illustrates an electrode assembly 300 that comprises a conductivesensing electrode 302. The conductive sensing electrode 302 may includea foundational layer (e.g., made of foam), an electrically conductiveelement (e.g., made of tin, silver-silver chloride, etc.) held inelectrical contact with the patient's skin, and a gel dispenser 304configured to dispense electrically conductive gel between theelectrically conductive element and the patient's skin. The conductivesensing electrode 302 may acquire ECG signals that are conditioned andprocessed by the ambulatory medical device to determine the patient'scardiac condition. This conditioning and processing generates ECG databased on the ECG signals. The ECG signals have an improved reliabilityover ECG signals acquired by dry sensing electrodes because of use ofgel.

The gel dispenser 304 is coupled to and under the control of a treatmentcontroller (e.g., the treatment controller 216). An electrolytic gellayer of the sensing electrode 302 is applied by the gel dispenser 304under control of the treatment controller during execution of thetreatment protocol. The gel dispenser 304 may include, for example, agel reservoir that is ruptured to dispose the gel between theelectrically conductive element of the sensing electrode 302 and theskin of the patient.

FIG. 4 illustrates another example of an electrode assembly 400 thatincludes a multi-function electrode 402 and a gel dispenser 404. Themulti-function electrode 402 may include a foundational layer (e.g.,made of foam), an electrically conductive element made of a metal (e.g.,made of tin, silver-silver chloride, etc.), and an electrolytic layer(e.g., made of hydrogel) that electrically couples the conductiveelement to the patient's skin. The multi-function electrode 402 mayacquire ECG signals that are conditioned and processed by the ambulatorymedical device to determine the patient's cardiac condition. Thisconditioning and processing generates ECG data based on the ECG signals.The ECG signals may have an improved reliability over ECG signalsacquired by dry sensing electrodes. The multi-function electrode 402 mayalso provide one or more therapeutic stimulation pulses to the skin ofthe patient.

The gel dispenser 404 is coupled to and under the control of thetreatment controller. In some examples of the electrode assembly 400,the electrolytic layer of the multi-function electrode 402 is applied bythe gel dispenser 404 under control of the treatment controller duringexecution of the treatment protocol. The gel dispenser 404 may include,for example, a gel reservoir that is ruptured to dispose the gel betweenthe electrically conductive element of the multi-function electrode 402and the skin of the patient.

FIG. 5 illustrates a therapy pad 500 that incorporates one or more ofthe elements of the therapy electrodes 114 described above withreference to FIG. 1. As shown in FIG. 5, the therapy pad 500 may includeboth a therapy electrode 502 and a sensing electrode 302. In someexamples, the therapy pad 500 is configured to dispose gel in a mannerthat prevents the gel from acting as a direct electrical connectionbetween the therapy electrode 502 and the electrode of the sensingelectrode 302. In some examples of the therapy pad 500, the geldispenser 504 operates under control of the treatment controller and,during execution of the treatment protocol, disposes a layer ofelectrically conductive gel between the therapy electrode 502 (and insome examples, the sensing electrode 302) and the skin of the patient.As shown in FIG. 5, the therapy pad 500 may include the gel dispenser304. In this example, the gel dispenser 304 is optional as indicated byits rendering in dashed line. As described above, the gel dispenser 304may dispose a layer of electrically conductive gel between the sensingelectrode 302 and the skin of the patient. In some examples, the metallayer of the therapy electrode 502 is used as a conductive sensingelectrode as well as a therapy electrode. In other examples, a portionof the therapy electrode 502 is electrically isolated from the remainderof the therapy electrode 502 and incorporates a distinct sensingelectrode, such as the sensing electrode 302. As described above, thesensing electrode 302 may acquire ECG signals that are conditioned andprocessed by the medical device to determine the patient's cardiaccondition. The therapy electrode 502 may provide one or more therapeuticstimulation pulses to the patient.

Although FIGS. 3-5 depict conductive sensing, multi-function, andtherapy electrodes, examples are not limited to these types ofelectrodes. For instance, some examples may use the same or differentpairs of dry sensing electrodes to acquire both the first and second ECGsignals. Other combinations will be apparent in view of the presentdisclosure. In addition, as described above with reference to FIGS. 1and 2, the electrode assemblies 300 and 400 and the therapy pad 500 mayinclude other types of sensors used to detect other physiologicparameters. For example, the electrode assemblies and therapy pad mayinclude PPG and/or accelerometric sensors that detect oxygen saturationof the patient's blood, patient respiration, and other patient movement.

The various example medical devices described above may execute one ormore monitoring and treatment processes that verify a cardiac arrhythmiacondition prior to administering a therapeutic stimulation pulse. FIG.6A illustrates one example of such a monitoring and treatment process600 executed in some examples. The monitoring and treatment process 600starts with a cardiac monitor 214 of an ambulatory medical device 100receiving 602 first ECG data based on first ECG signals acquired by afirst pair of electrodes. This first pair of electrodes may include oneor more sensing electrodes (e.g., sensing electrodes 112 or ECGelectrodes 222), one or more therapy electrodes, and/or one or moremulti-function electrodes configured to include sensing capability andtherapy capability (i.e., the administration of therapeutic stimulationpulses). In some examples of act 602, the cardiac monitor 214 receivesother data indicative of other patient physiologic parameters, such asoxygen saturation, respiration, and/or other movement.

Next, the cardiac monitor attempts to detect abnormalities 604 in thefirst ECG data and/or the other patient physiologic data by executing anabnormality detection process. This abnormality detection process mayinclude various sub-processes, as described further below with referenceto Table 1 and FIGS. 7 and 8. Where the cardiac monitor does not detect606 an arrhythmia condition, the cardiac monitor returns to receiving602 first ECG data. However, upon detecting 606 that the patient isexperiencing an arrhythmia condition, the cardiac monitor records 608 aninitial arrhythmia declaration (e.g., by storing one or more bits at aspecific memory location) and initiates 610 a treatment protocol basedon the type of arrhythmia condition detected.

In some examples, initiation 610 of the treatment protocol includesissuance of an alarm (e.g., an auditory alarm, a tactile alarm, a visualalarm, or a combination thereof) of an impending therapeutic stimulationpulse. This alarm enables the patient to correct an otherwise erroneousarrhythmia declaration and enables people proximate to the patient totake appropriate action (e.g., avoid physical and electricallyconductive contact with the patient, call medical support staff, etc.).

In some examples the treatment protocol includes identifying thearrhythmia condition detected and selecting a therapeutic stimulationpulse best suited to correct the detected arrhythmia condition.Parameters for the therapeutic stimulation pulse to be applied that canvary between different types of arrhythmia condition include theperiodicity with which a therapeutic stimulation pulse is delivered, avoltage, a current, a phase, a waveform, and a duration, among otherparameters. In some examples, the treatment protocol includes provision,by a treatment controller (e.g., the treatment controller 216), of oneor more control signals to associated processors, circuitry, and/orsystems of the ambulatory medical device 100 to initiate 610 a treatmentprotocol for the provision to the patient of the selected therapeuticstimulation pulse.

In one example, after initiation 610 of the treatment protocol, thetreatment controller controls, via a gel dispenser and associatedcircuitry, optional application 612 of conductive gel between thepatient's skin and one or more of a first sensing electrode pair, asecond sensing electrode pair, a multi-function electrode pair, atherapy electrode pair or any combination thereof. As described above,conductive gel can improve the electrical contact (and thereforeconductivity) between an electrode and the skin of the patient, thusimproving the therapeutic quality of the applied stimulation pulse whilealso reducing the risk of injury (such as topical burning or scorching)to the patient. The optional application 612 of conductive gel can alsoimprove the quality (e.g., signal to noise ratio) of a second ECG signaldetected by one or more of a first sensing electrode pair, a secondsensing electrode pair, and/or a multi-function electrode pair.

The conductive gel may be applied 612 in response to an instruction fromthe treatment controller to gel deployment circuitry. Upon receiving theinstruction (e.g., a control signal) from the treatment controller, thegel deployment circuitry causes at least one gel dispenser to applyconductive gel between at least one of a first sensing electrode pair, asecond sensing electrode pair, and a multi-function electrode pair andthe skin of the patient prior to acquiring second ECG signals, asdescribed herein.

Regardless of whether gel is applied 612, the monitoring and treatmentprocess 600 continues with the treatment controller receiving 614 secondECG data based on second ECG signals acquired by a second pair ofelectrodes. This second pair of electrodes may be in contact with theconductive gel and may include one or more sensing electrodes (e.g.,sensing electrode pairs 112 or ECG electrodes 222), one or more therapyelectrodes, and/or one or more multi-function electrodes configured toinclude sensing capability and therapy capability (i.e., theadministration of therapeutic stimulation pulses). When using distinctelectrode pairs to detect and acquire the first ECG signals and thesecond ECG signals, the first sensing electrode pair and the secondsensing electrode pair may rely on different electrodes to detect theECG signals. In an example, the first pair of sensing electrodesoperates using a dry sensing electrode where the second pair of sensingelectrodes (or therapy or multi-function electrodes) operates using aconductive sensing electrode. In an example, the arrhythmia conditiondetection mechanism used by the second electrode pair is selected sothat it has a higher reliability than that used by the first electrodepair, as described above.

Next, the treatment controller attempts to verify 616 the declaredarrhythmia 616 using the second ECG data by executing an arrhythmiaverification process. For example, the second process to verify thearrhythmia can be initiated as soon as one second after the initialdeclaration of the arrhythmia. In some examples, the second process toverify the arrhythmia can be initiated in time periods of between around2 to 10 seconds, 10 to 30 seconds, 30 to 45 seconds, 45 seconds to 60seconds, or 60 seconds to 120 seconds after the initial declaration ofthe arrhythmia. In some cases, if the patient responds via one or moreresponse buttons, or otherwise is detected by the treatment controlleras being conscious, the initiation of the second process to verify thearrhythmia can be delayed by an additional period of time (e.g., anadditional 30 to 45 seconds) beyond the time periods specified above.One or more of these time periods can be preconfigured during an initialsetup of the device (e.g., by a technician or a patient servicerepresentative). For instance, the time periods can be stored in memoryor other data storage as one or more user-configurable values. In someexamples, these one or more user-configurable values include a firstvalue and a second value. The first value specifies a time period thatthe treatment controller is configured to wait between the initialdeclaration of the arrhythmia and initiation of the second process. Thesecond value specifies a time period by which the treatment controlleris configured to delay initiation of the second process in response todetecting that the patient is conscious (e.g., by a user action such aswhen the patient presses the one or more response buttons).

The arrhythmia verification process may include various sub-processes,as described with reference to Table 1 and FIGS. 7 and 9. In an example,the verification 616 of the second ECG data results in a more reliabledetermination of whether or not the patient is experiencing anarrhythmia condition. Furthermore, as indicated above, the phrases “morereliable,” “higher reliability,” and “improved reliability” can includeusing different processing algorithms and/or statistical analysistechniques that produce an analysis of the second ECG signal having anincreased statistical confidence level compared to the analysisgenerated using the first ECG signal. For instance, in some examples theanalyses may use stricter criteria for identifying an arrhythmiacondition, may process longer samples of the second ECG data than thesamples of first ECG data previously processed, may process more samplesof the second ECG data than the samples of the first ECG data previouslyprocessed, and/or may process an overall amount of second ECG data thatis greater than the amount of first ECG data previously processed.Additionally or alternatively, in an example, reliability is improved byselecting different ECG circuitry (i.e., a sensor and circuitry used foracquiring an ECG signal from a patient) or causing a tighter fit betweenthe second electrode pair and the patient (e.g., by tightening the belt150 of the ambulatory medical device).

Where the treatment controller refutes or otherwise fails to verify 618the declared arrhythmia condition, the treatment controller aborts ordelays 620 the treatment protocol. In some examples, upon not verifying618 an arrhythmia condition, the delivery of a therapeutic stimulationpulse is delayed by a predefined time period (e.g., at least 30 seconds,at least 45 seconds, etc.). If via execution of the act 618, or duringthe delay period, the treatment controller determines that normal sinusrhythm has returned in the patient, the treatment protocol can beaborted, and the medical device can return to a monitoring state via thecardiac monitor. Thus, in these situations, the treatment controlleraborts providing any therapeutic stimulation pulse to the patient. Uponaborting or delaying 620 the treatment protocol, the treatmentcontroller returns control to the cardiac monitor, which receives 602first ECG data, as described above. Alternatively or additionally, insome examples, second ECG signals may also be monitored 614 during thedelay or after aborting 620.

However, upon verifying 618 (e.g., prior to, during, after delaying 620treatment) the arrhythmia declaration, the treatment controller delivers622, in an attempt to restore a normal rhythm to the patient's heart,one or more therapeutic stimulation pulses as selected in response tothe type of arrhythmia condition detected. For example, upon detectionby the treatment controller of ventricular fibrillation in the patient,the treatment controller can deliver 622 a defibrillating therapeuticstimulation pulse to the heart of the patient. For example, upondetection by the treatment controller of bradycardia in the patient, thetreatment controller can deliver 622 a series of pacing therapeuticstimulation pulses to the heart of the patient. The treatment controllercan provide other types of therapeutic stimulation pulses to the patentdepending on the arrhythmia condition detected.

After delivery 622 of the therapy, the treatment controller analyzes thefirst or the second ECG signals to determine 624 whether a “normal”heart rhythm (i.e., not an arrhythmia condition) has been restored. If anormal rhythm has been restored, the treatment controller returnscontrol to the cardiac monitor. However, if a normal rhythm has not beenrestored, the treatment controller determines whether or not treatmentshould be continued 626. This determination may be made based on anumber of factors, including, for example, whether execution of thetreatment protocol has continued for longer than a threshold duration orfor more than a threshold number of cycles. Also, this determination maybe made based on whether the ambulatory medical device has sufficientresources available to continue execution of the treatment protocol(e.g., whether sufficient battery power remains). If treatment can becontinued 626, the treatment protocol may optionally be adjusted 628 to,for example, change the type of therapeutic stimulation pulse providedto the patient (e.g., change from a defibrillation pulse to a pacingpulse) or change the electrical characteristics of a same type oftherapeutic stimulation pulse previously provided to the patient (e.g.,increase/decrease energy, increase/decrease duration, etc.). If thetreatment cannot be continued 626 the monitoring and treatment process600 ends.

FIG. 6B provides an illustration of a monitoring and treatment protocol650 (also called a treatment alarm sequence). The treatment protocol 650may be executed by an ambulatory medical device (e.g., the ambulatorymedical device 100). As shown, the protocol 650 includes 7 milestonesthat occur within 1 minute of abnormality detection. However, the lengthof the protocol 650 can be longer or shorter depending on certainfactors. For example, if the potential arrhythmia rhythm is identifiedas a VT rhythm, a default response time for the patient may be 60seconds, which can be adjusted to be in a range of 60 to 180 seconds.For example, if the potential arrhythmia rhythm is identified as a VFrhythm, a default response time may be 25 seconds, which can be adjustedto be in a range of 25 to 60 seconds. Thus, the duration of the protocol650 can be adjusted to accommodate for these response times. If atreatment alarm sequence is ongoing, in some examples, based on thearrhythmia verification processes described herein the treatmentcontroller can hasten the application of the defibrillation shock sothat the shock is delivered sooner than the default of configured time.Otherwise, the treatment controller can delay the shock, for example, anadditional 25-45 seconds.

In the example protocol 650, at milestone 1, a cardiac monitor (e.g.,the cardiac monitor 214) of the ambulatory medical device declares anarrhythmia based on a first process, an abnormality detection process.At milestone 2, which occurs approximately 5 seconds after milestone 1,the cardiac monitor initiates a treatment protocol and passes control ofthe ambulatory medical device to a treatment controller (e.g., thetreatment controller 216) to complete execution of the treatmentprotocol. In some examples, as part of initiating the treatment protocolat milestone 2, the cardiac monitor issues an alarm. This alarm may bevisual, auditory, or tactile in nature. For example, the alarm may be asiren that continues throughout execution of the treatment protocol.

At milestone 3, which occurs approximately 5 seconds after milestone 2,the treatment controller instructs the mechanism outputting the alarm toincrease the alarm's magnitude (e.g., increase the volume of the siren).At milestone 4, which occurs approximately 5 seconds after milestone 3,the treatment controller provides an audio prompt to the patient thatinstructs the patient to press the response buttons to delay treatment.At milestone 5, which occurs approximately 5 seconds after milestone 4,the treatment controller instructs the gel deployment circuitry todeploy gel. At milestone 6, which occurs approximately 4 seconds aftermilestone 1, the treatment controller issues an audio prompt tobystanders that instructs the bystanders to not interfere with thetreatment protocol. At milestone 7, which occurs approximately 4 secondsafter milestone 6, the treatment controller instructs the therapydelivery circuitry to deliver one or more therapeutic stimulation pulsesto the patient. As shown in FIG. 6B, the treatment protocol concludeswith restoration of a normal sinus rhythm and the treatment controllerinitiates a monitoring process and passes control of the ambulatorymedical device back to the cardiac monitor.

In some examples, the treatment controller verifies the arrhythmia aftermilestone 5 and before milestone 7, based on one or more secondprocesses, e.g., arrhythmia verification processes. To do so, thetreatment controller may execute any of the arrhythmia verificationprocesses described herein.

The abnormality detection and arrhythmia verification processes 604 and616 can be distinct processes that vary between examples. As such, theabnormality detection and arrhythmia verification processes may includea variety of sub-processes that analyze ECG signals by processing ECGdata representative of the ECG signals. For example, the arrhythmiaverification process may be an abbreviated version of the abnormalitydetection process and may include fewer sub-processes than theabnormality detection process in the interest of faster execution. In anexample, sub-processes for the abnormality detection process may includeone or more of the following sub-processes: a fast Fourier transform(FFT) to analyze ECG signal frequency components; a heart rate analyzer;a spectrum analyzer to analyze patterns within a plurality of ECG signalwavelengths; an ECG morphology analyzer to compare the ECG signal withbaseline ECG signals, and various artifact sensors and associatedprocesses to determine whether an ECG signal is artificial (e.g., frompoor contact with the skin of the patient). These sub-processes aredescribed in U.S. Pat. No. 5,944,669, titled “Apparatus and Method forSensing Cardiac Function,” which is hereby incorporated herein byreference in its entirety.

In addition, the abnormality detection process and/or the arrhythmiaverification process can include one or more confidence sub-processes(e.g., a confidence sub-process implemented by at the cardiac monitorand/or the treatment controller) that determine a confidence level inthe declaration of an abnormality or verification of an arrhythmiacondition. For example, such a confidence process can be a process fordistinguishing a cardiac event from noise in an ECG signal. As anexample, such a confidence sub-process may sample portions of the ECGsignals in segmented blocks (e.g., one second ECG strips) and determineusing, e.g., a machine learning system, whether the samples can beclassified as noise or a cardiac event. The confidence process mayanalyze a portion of the ECG signals, e.g., 10-30 seconds of thereceived ECG signals, prior to declaring a confidence level in thearrhythmia declaration. In other examples, smaller amounts of ECGsignals may be considered in the analysis (e.g., ECG signals acquiredover a time period of less than 10 seconds, ECG signal acquired over atime period between 1 and 10 seconds, etc.). Regardless of the amount ofECG data processed by the confidence sub-process, the resultingconfidence value may be evaluated by, for example, comparing the valueto a threshold value or set of threshold values to determine whether theECG data represents a cardiac event or noise.

By way of example, if an abnormality is detected by the cardiac monitorin executing one or more of the sub-processes of the abnormalitydetection process, ECG signals in which the abnormality was detected canbe sent to a noise detection process. The noise detection process may beconfigured to process these ECG signals to determine whether thedetected abnormality is an arrhythmia condition or is caused by noise.For example, the output of the noise detection process may be in theform of a flag that is set to indicate whether or not an arrhythmiacondition can be declared due to the absence or presence of noise.Additional details regarding the foregoing noise detection process canbe found in U.S. Patent Application Publication No. 2016/0000349, titled“SYSTEM AND METHOD FOR DISTINGUISHING A CARDIAC EVENT FROM NOISE IN ANELECTROCARDIOGRAM (ECG) SIGNAL,” which is hereby incorporated herein inby reference its entirety.

Regardless, one or more of these sub-processes (among others identifiedin U.S. Pat. No. 5,944,669) initially included in the abnormalitydetection process can be omitted in the arrhythmia verification process.For example, while ECG signals representative of heart rate and heartbeat morphology may be analyzed, an FFT of a heart beat pattern may beomitted, thus reducing the time required for the verification analysis.In another example, arrhythmia verification may operate on less ECG data(e.g., based on ECG signals acquired over a time period of between 5 and10 seconds) than abnormality detection (e.g., based on ECG signalsacquired over a time period of between 10 and 50 seconds). One advantageof omitting certain sub-processes is that a second duration of time usedto execute the arrhythmia verification process is less than a firstduration of time used execute the abnormality detection process. As withother components described herein, instead of or in addition to one ofmore processors, some or all of the abnormality detection and arrhythmiaverification processes may be executed by specialized circuitry (e.g.,an ASIC or FPGA).

Table 1 illustrates one example implementation of the abnormalitydetection and arrhythmia verification processes.

TABLE 1 Abnormality Arrhythmia Arrhythmia Detection VerificationVerification Abnormality Detection Process Sub- Process Process Sub-Process processes Output Processes Output Fast Fourier transform (FFT)to analyze ECG Output 1: Execute ECG Output 1: signal frequencycomponents Declare morphology Arrhythmia arrhythmia analyzer tocondition condition compare the verified ECG signal with baseline ECGsignals Execute heart rate analyzer Output 2: Execute heart Output 2:Arrhythmia rate analyzer Arrhythmia Execute spectrum analyzer to analyzecondition not Execute condition not patterns within a plurality of ECGsignal declared confidence verified wavelengths process to Execute ECGmorphology analyzer to confirm that compare the ECG signal with baselineECG abnormal event signals is an arrhythmia condition (e.g., VT/VF)Execute confidence process to confirm that abnormal event is anarrhythmia condition (e.g., VT/VF) Analyze pulse ox data to determinewhether the patient's blood oxygen saturation is above a configurablethreshold value, within a configurable range of values, or has deviatedfrom a baseline beyond a threshold value. Analyze respiration data todetermine whether the patient's respiration is above a configurablethreshold value, within a configurable range of values, or has deviatedfrom a baseline beyond a threshold value. Analyze patient movement datato determine whether the patient's movement is above a configurablethreshold value, within a configurable range of values, or has deviatedfrom a baseline beyond a threshold value.

Examples that include an abnormality detection process and/or anarrhythmia verification process are not limited with regard to thesub-processes included in each process. For instance, in one example,the arrhythmia verification process includes only an FFT to analyze ECGsignal frequency components. Alternatively or additionally, otherexamples may include other sub-processes within either or both of theabnormality detection process and the arrhythmia verification process.

Optionally, as shown in Table 1, the abnormality detection andarrhythmia verification processes may also analyze other data whendetecting and verifying. For example, the first or second pair ofsensing electrodes (and other pairs of sensing electrodes andmulti-function electrodes described herein) may also include at leastone of a heart sounds sensor 224 and a tissue fluid monitor 226. Thecardiac monitor may access data descriptive of one or more signalsacquired by the heart sounds sensor 224 and/or the tissue fluid monitor226 to further analyze whether the patient is experiencing an arrhythmiacondition and determining what type of arrhythmia condition the patientis experiencing.

For instance, in some examples, the first process or the abnormalitydetection process includes non-ECG based sub-processes as a replacementof, or a supplement to, the ECG based sub-processes described above. Forinstance, in one example, the abnormality detection process includes oneor more of a pulse ox sub-process, a respiration sub-process, and apatient movement sub-process. These sub-processes may be consistentlyexecuted as part of the abnormality detection process or may beconditionally executed based on the outcome of the other sub-processes.For instance, in certain examples, the pulse ox, the respiration, and/orthe patient movement sub-processes are executed only where the ECG basedsub-processes return assessments that are in conflict. In theseexamples, the pulse ox, the respiration, and/or the patient movementsub-processes may contribute to determining whether an arrhythmiacondition is declared by the abnormality detection process. Forinstance, the abnormality detection process may determine whether anarrhythmia condition is declared using a voting process that includesall of the sub-processes as described further below with reference toFIG. 7.

In certain examples, the pulse ox sub-process analyzes PPG dataindicative of the oxygen saturation of the patient's blood to determinewhether the patient is experiencing an arrhythmia or other abnormality.This analysis may include comparing the patient's current oxygensaturation level to a previously recorded baseline or to one or morepredefined threshold values. For instance, in one example where thepulse ox sub-process compares the patient's current oxygen saturationlevel to a baseline, the pulse ox sub-process determines that thepatient is experiencing an arrhythmia where the patient's current oxygensaturation level deviates from the baseline by 20% or more. The baselinemay be configurable between 10% and 90% and therefore may vary betweenexamples. In another example where the pulse ox sub-process compares thepatient's current oxygen saturation level to one or more predefinedthreshold values, the pulse ox sub-process determines that the patientis experiencing an arrhythmia where the patient's current oxygensaturation level transgresses at least one of the threshold values(e.g., 95%). This value may be configurable and therefore may varybetween examples.

In some examples, the respiration sub-process analyzes accelerometerdata indicative of the patient's respiration rate to determine whetherthe patient is experiencing an arrhythmia or other abnormality. Thisanalysis may include comparing the patient's current respiration rate toa previously recorded baseline or to one or more predefined thresholdvalues. For instance, in one example where the respiration sub-processcompares the patient's current respiration rate to a baseline, therespiration sub-process determines that the patient is experiencing anarrhythmia where the patient's current respiration rate deviates fromthe baseline by 10% or more. The baseline may be configurable between10% and 90% and therefore may vary between examples. In another examplewhere the respiration sub-process compares the patient's currentrespiration rate to one or more predefined threshold values, therespiration sub-process determines that the patient is experiencing anarrhythmia where the patient's current respiration rate transgresses atleast one of the threshold values (e.g., 12 or 25 breaths per minute).This value may be configurable and therefore may vary between examples.

In some examples, the movement sub-process analyzes accelerometer dataindicative of the patient's movement to determine whether the patient isexperiencing an arrhythmia or other abnormality. This analysis mayinclude comparing the patient's current movement to a previouslyrecorded baseline or to one or more predefined threshold values. Forinstance, in one example where the movement sub-process compares thepatient's current movement to a baseline, the movement sub-processdetermines that the patient is experiencing an arrhythmia where thepatient's current movement rate deviates from the baseline by 30% ormore. The baseline may be configurable between 10% and 90% and thereforemay vary between examples. In another example where the movementsub-process compares the patient's current movement to one or morepredefined threshold values, the movement sub-process determines thatthe patient is experiencing an arrhythmia where the patient's currentmovement rate transgresses at least one of the threshold values (e.g.,substantially no movement). This value may be configurable and thereforemay vary between examples. One example of the movement sub-process usedto supplement ECG based arrhythmia detection processes is described inU.S. Pat. No. 7,974,689, titled “Wearable Medical Treatment Device withMotion/Position Detection,” which is hereby incorporated herein byreference in its entirety. The movement sub-process described in U.S.Pat. No. 7,974,689 determines whether the patient is exhibitingsubstantial movement and uses that determination to inform its ultimatedetermination as to whether the patient is experiencing an arrhythmia.

The arrhythmia detection process is designed to evaluate several rateinputs simultaneously to determine the patient's heart rate. Thearrhythmia detection process uses two QRS detector sub-processes, one toan electrode pair, to provide independent assessments of heart rate. ECGsignal frequencies are also analyzed using an FFT sub-process, whichdecomposes an analog waveform into its frequency components and allowsinput signal analysis in the frequency domain. The FFT sub-processoutput is analyzed to determine the strongest frequency componentindicative of heart rate. The FFT analysis often provides the bestindication of heart rate, specifically during ventricular tachycardia(VT) or ventricular fibrillation (VF). Finally, a morphology analysissub-process is also used to determine the heart rate.

The arrhythmia detection process then applies logical weights based oncomparing leads, signal quality, and historic rate values in order todetermine the best inputs to accurately monitor the patient's heartrate. For example, if the heart rate from the two QRS detectorsub-processes do not match, less weight is applied to these inputs andgreater weight is applied to other sources.

Once the arrhythmia detection process determines the best combination offactors to assess heart rate, the heart rate is then categorized asbelow the VT threshold, above the VT threshold but below the VFthreshold, or above the VF threshold. These thresholds are programmedfor the patient during setup. If the rate exceeds the VT or the VFthreshold, the arrhythmia detection process then proceeds to amorphology analysis sub-process comparing the patient's normal rhythmbaseline template obtained during device setup to the current QRSmorphology.

The arrhythmia detection process also applies a confidence sub-processas part of the process for deciding to treat or not to treat anarrhythmia. The confidence sub-process is the sum of the individuallyweighted input factors of heart rate, morphology, response button use,and signal quality. The input factors can contribute positively ornegatively to the confidence. If an input factor is deemed unreliable,its weight can be lessened or redistributed entirely to other factors.

Once an arrhythmia is declared, the confidence sub-process must decideif the rhythm is treatable based on the duration or persistence of thearrhythmia. If a value of confidence generated by the confidencesub-process falls below a specified level, the treatment protocol isterminated and the system reverts to monitoring for a new arrhythmia.

For example, if a patient uses the response buttons after hearing thealarms and the heart rate slows, the confidence value would decrease. Ifthe patient releases the response buttons and the heart rate increasesor becomes abnormal, the confidence value would increase. Any one and/orall of the sub-processes defined by the arrhythmia detection process canbe used within either or both of the abnormality detection andarrhythmia verification processes.

In some examples, the abnormality detection process and/or thearrhythmia verification process are each voting processes that makedeterminations based on a summary of the sub-processes they execute.Further the abnormality detection process and/or the arrhythmiaverification process may be configuration data driven processes thatreference configuration data parameters which specify sub-processes toexecute. FIG. 7 illustrates one example of a voting process 700 that isconfiguration data driven and that, therefore, can be used to implementthe abnormality detection process or arrhythmia verification process.

As shown in FIG. 7, the voting process 700 starts in act 702 with avoting controller (e.g., either the cardiac monitor or the treatmentcontroller) identifying, within configuration data, a list of one ormore sub-processes to execute as part of the voting process 700. Thisconfiguration data may be stored, for example, in the data storage 204of the medical device controller 120. The list of sub-processes mayinclude any of the sub-processes listed in Table 1 above or elsewhere inthis disclosure. In some examples, in addition to storing identifiers ofthe sub-processes to include in the voting process 700, theconfiguration data also stores weights to be applied to the output (or“vote”) of each sub-process and one or more threshold values used tojudge the overall outcome of the voting process.

In act 704, voting controller executes the next unexecuted sub-processfrom the list of one or more sub-processes generated in the act 702. Inact 706, the voting controller stores the result of the sub-processexecuted in the act 704. In act 708, the voting controller determineswhether any unexecuted sub-processes remain on the list of one or moresub-processes generated in the act 702. If so, the voting controllerreturns to the act 702. If no unexecuted sub-processes remain, in act710 the voting controller identifies the collective determination of thesub-processes using the one or more threshold values stored in theconfiguration information and the voting process 700 ends.

To increase speed and decrease configurability, other examples implementthe abnormality detection process and/or the arrhythmia verificationprocess to include a fixed set of sub-processes. FIG. 8 illustrates anabnormality detection process 800 as implemented in these examples. FIG.9 illustrates an arrhythmia verification process 900 as implemented inthese examples.

As shown in FIG. 8, the abnormality detection process 800 starts in act802 with the cardiac monitor executing an FFT analyzer that generates anFFT of the first ECG data to compare frequency components to a baselinefor the patient to determine whether the patient is suffering from anarrhythmia condition. In act 804, the cardiac monitor executes a heartrate analyzer to compare the patient's heart rate to a baseline for thepatient to determine whether the patient is suffering from an arrhythmiacondition. In act 806, the cardiac monitor executes a spectrum analyzerto determine whether patterns within a plurality of wavelengths indicatethat the patient is suffering from an arrhythmia condition. In act 808,the cardiac monitor executes a morphology analyzer to compare themorphology indicated by the first ECG data to a benchmark establishedfor the patient to determine whether the patient is suffering from anarrhythmia condition. In act 810, the cardiac monitor executes aconfidence process to establish an overall confidence that the detectedabnormal event is an arrhythmia condition (and not, for example, noise).In act 812, the cardiac monitor identifies the collective determinationof the sub-processes executed in acts 802-810 and the abnormalitydetection process 800 ends. In some examples, the determination of theact 812 is made by summarizing the output of the sub-processes (e.g.,summing their return values) and comparing the summary to one or morethreshold values.

As shown in FIG. 9, the arrhythmia verification process 900 starts inact 902 with the treatment controller executing a heart rate analyzer tocompare the patient's heart rate to a baseline for the patient todetermine whether the patient is suffering from an arrhythmia condition.In act 904, the treatment controller executes a morphology analyzer tocompare the morphology indicated by the first ECG data to a benchmarkestablished for the patient to determine whether the patient issuffering from an arrhythmia condition. In act 906, the treatmentcontroller identifies the collective determination of the sub-processesexecuted in acts 902 and 904 and the arrhythmia verification process 900ends. In some examples, the determination of the act 906 is made bysummarizing the output of the sub-processes (e.g., summing their returnvalues) and comparing the summary to one or more threshold values.

As described above, in some examples, the abnormality detection processand the arrhythmia verification process execute different sets ofsub-processes. However, in other examples, the abnormality detectionprocess and the arrhythmia verification process execute a common set ofsub-processes. Thus, the examples described herein are not limited toabnormality detection or arrhythmia verification processes that executedifferent or common sets of sub-processes. Nor are the examplesdescribed herein limited to a specific set of sub-processes.

Example Configurations

Some examples advantageously leverage the features disclosed above toprovide for an ambulatory medical treatment device that utilizesdistinct sensing electrodes in execution of abnormality detection andarrhythmia verification processes. Examples of this ambulatory medicaltreatment device and the processes it executes are illustrated by FIGS.10 and 11.

As shown, FIG. 10 includes a medical device 1000 that is external,ambulatory, and wearable by the patient 102. The medical device 1000includes many of the components of the medical device 100 describedabove. For example, the medical device 1000 includes the garment 110,the sensing electrode pairs 112, the therapy electrode pair 114, themedical device controller 120, the connection pod 130, the patientinterface pod 140, and the belt 150. The therapy electrode pair 114 isconfigured to couple externally to a skin of the patient 102 and toprovide one or more therapeutic stimulation pulses to a heart of thepatient 102 during execution of a treatment protocol.

In addition, the medical device 1000 includes a distinct sensingelectrode pair 1012 that is configured to couple externally to the skinof the patient 102 and to acquire ECG signals. In some examples, thisdistinct pair of electrodes 1012 includes conductive electrodes.However, any one of the electrodes of the pair of electrodes 1012 may beany of the conductive electrodes or dry electrodes described herein.

In some examples, the medical device 1000 is configured to acquire firstECG signals via the electrode pairs 112 and to acquire second ECGsignals via the pair of electrodes 1012. In these examples, second ECGdata based on the second ECG signals has an improved reliability overfirst ECG data based on the first ECG signals.

In some examples, the medical device controller 120 of the medicaldevice 1000 includes a cardiac monitor (e.g., the cardiac monitor 214)and a treatment controller (e.g., the treatment controller 216). Inthese examples, the cardiac monitor and treatment controller areconfigured to execute monitoring and treatment processes that includeabnormality detection and arrhythmia verification processes. At leastone example monitoring and treatment process 1100 that the cardiacmonitor and the treatment controller are configured to execute isdescribed further below with reference to FIG. 11.

As shown in FIG. 11, the monitoring and treatment process 1100 includesthe actions of the monitoring and treatment process 600. However, manyof the details of the monitoring and treatment process 600 are omittedfrom the following description of the monitoring and treatment process1100 for the sake of brevity. As shown in FIG. 11, the monitoring andtreatment process 1100 starts with the cardiac monitor receiving 1102first ECG data based on first ECG signals acquired by at least one firstpair of sensing electrodes. In this example, the at least one first pairof sensing electrodes includes the sensing electrode pairs 112. In someexamples, the act of receiving 1102 the first ECG data includes one ormore of the acts described above with reference to the act 602.

Next, the cardiac monitor attempts to detect abnormalities 604 in thefirst ECG data by executing an abnormality detection process asdescribed above. Where the cardiac monitor does not detect 606 anarrhythmia condition of the patient, the cardiac monitor returns toreceiving 1102 first ECG data. However, upon detecting 606 that thepatient is experiencing an arrhythmia condition, the cardiac monitorrecords 608 an initial arrhythmia declaration and initiates 610 atreatment protocol.

In one example, after initiation 610 of the treatment protocol, thetreatment controller controls, via a gel dispenser and associatedcircuitry, optional application 1112 of conductive gel between thepatient's skin and a second pair of electrodes (e.g., the electrode pair1012). The conductive gel may be applied between the second pair ofelectrodes and the skin of the patient prior to acquiring second ECGsignals, as described herein. In some examples, the act of applying 1112the conductive gel includes one or more of the acts described above withreference to the act 612.

Regardless of whether gel is applied 1112, the monitoring and treatmentprocess 1100 continues with the treatment controller receiving 1114second ECG data based on second ECG signals acquired by the second pairof electrodes. In this example, the second pair of electrodes is thepair of sensing electrodes 1012. Where this second pair of electrodes isused, the second ECG signals (and resulting data) benefit from increasedreliability due to increased accuracy and precision of conductivesensing electrodes. In some examples, the act of receiving 1114 thesecond ECG data includes one or more of the acts described above withreference to the act 614.

Next, the treatment controller attempts to verify 616 the declaredarrhythmia using the second ECG data by executing an arrhythmiaverification process. In an example, the verification 616 of the secondECG data results in a more reliable determination of whether or not thepatient is experiencing an arrhythmia condition.

Where the treatment controller fails to verify 618 the declaredarrhythmia condition, the treatment controller aborts or delays 620 thetreatment protocol. Upon verifying 618 the arrhythmia declaration, thetreatment controller delivers 622, in an attempt to restore a normalrhythm to the patient's heart, one or more therapeutic stimulationpulses as selected in response to the type of arrhythmia conditiondetected. This verification 618 may occur during a period of time inwhich treatment has been delayed 620 or may occur prior to any delay 620of treatment.

After delivery 622 of the therapy, the treatment controller analyzes thesecond ECG signals to determine 624 whether a “normal” heart rhythm(i.e., not an arrhythmia condition) has been restored. If a normalrhythm has been restored, the treatment controller returns control tothe cardiac monitor. However, if a normal rhythm has not been restored,the treatment controller determines whether or not treatment should becontinued 626. If treatment can be continued 626, the treatment protocolmay optionally be adjusted 628 to, for example, change the type oftherapeutic stimulation pulse provided to the patient. If the treatmentcannot be continued 626, the monitoring and treatment process 1100 ends.

Some examples advantageously leverage the features disclosed above toprovide for an ambulatory medical treatment device that utilizes one ormore pairs of sensing electrodes in execution of an abnormalitydetection process and one or more pairs of multi-function electrodes inexecution of an arrhythmia verification process. Examples of thisambulatory medical treatment device and the processes it executes areillustrated by FIGS. 12 and 13.

As shown, FIG. 12 includes a medical device 1200 that is external,ambulatory, and wearable by the patient 102. The medical device 1200includes many of the components of the medical device 100 describedabove. For example, the medical device 1200 includes the garment 110,the sensing electrode pairs 112, the medical device controller 120, theconnection pod 130, the patient interface pod 140, and the belt 150. Thesensing electrode pairs 112 are configured to couple externally to askin of a patient and to acquire first ECG signals to detect anarrhythmia condition of the patient 102.

In addition, the medical device 1200 includes a pair of multi-functionelectrodes 1214 comprising multi-function electrodes 1214 a and 1214 b.Each multi-function electrode 1214 a and 1214 b of the multi-functionelectrode pair 1214 is configured to couple externally to the skin ofthe patient 102, to provide one or more therapeutic stimulation pulsesto the heart of the patient 102 during execution of a treatmentprotocol, and to acquire second ECG signals to verify the arrhythmiacondition of the patient 102. In some examples, each multi-functionelectrode 1214 a and 1214 b of the multi-function electrode pair 1214includes a therapy electrode and a conductive sensing electrode. In someexamples, the therapy electrode and the sensing electrode are switchedbetween sensing and therapy circuitry included in the medical device1200 to implement sensing and therapy modes and functionality. In someexamples, each multi-function electrode 1214 a and 1214 b of themulti-function electrode pair 1214 includes a multi-function electrode402. In some examples, each multi-function electrode 1214 a and 1214 bof the multi-function electrode pair 1214 is disposed within a therapypad, such as the therapy pad 500 illustrated in FIG. 5 above or asdescribed above with reference to FIG. 1.

In some examples, the medical device 1200 is configured to acquire firstECG signals via the sensing electrode pair 112 and to acquire second ECGsignals via the multi-function electrode pair 1214. In these examples,second ECG data based on the second ECG signals has an improvedreliability over first ECG data based on the first ECG signals.

In some examples, the medical device controller 120 of the medicaldevice 1200 includes a cardiac monitor (e.g., the cardiac monitor 214)and a treatment controller (e.g., the treatment controller 216). Inthese examples, the cardiac monitor and treatment controller areconfigured to execute monitoring and treatment processes that includeabnormality detection and arrhythmia verification processes. At leastone example monitoring and treatment process 1300 that the cardiacmonitor and the treatment controller are configured to execute isdescribed further below with reference to FIG. 13.

As shown in FIG. 13, the monitoring and treatment process 1300 includesthe actions of the monitoring and treatment process 600. However, manyof the details of the monitoring and treatment process 600 are omittedfrom the following description of the monitoring and treatment process1300 for the sake of brevity. As shown in FIG. 13, the monitoring andtreatment process 1300 starts with the cardiac monitor receiving 1302first ECG data based on first ECG signals acquired by sensingelectrodes. In this example, these sensing electrodes include theelectrode pairs 112. In some examples, the act of receiving 1302 thefirst ECG data includes one or more of the acts described above withreference to the act 602.

Next, the cardiac monitor attempts to detect abnormalities 604 in thefirst ECG data by executing an abnormality detection process asdescribed above. Where the cardiac monitor does not detect 606 anarrhythmia condition of the patient, the cardiac monitor returns toreceiving 1302 first ECG data. However, upon detecting 606 that thepatient is experiencing an arrhythmia condition, the cardiac monitorrecords 608 an initial arrhythmia declaration and initiates 610 atreatment protocol.

In one example, after initiation 610 of the treatment protocol, thetreatment controller controls, via a gel dispenser and associatedcircuitry, application 1312 of conductive gel between the patient's skinand a second pair of electrodes (e.g., the multi-function electrode pair1214). The conductive gel may be applied between the second pair ofelectrodes and the skin of the patient prior to acquiring second ECGsignals, as described herein. In some examples, the act of applying 1312the conductive gel includes one or more of the acts described above withreference to the act 612.

Regardless of whether gel is applied 1312, the monitoring and treatmentprocess 1300 continues with the treatment controller receiving 1314second ECG data based on second ECG signals acquired by the second pairof electrodes. In this example, the second pair of electrodes is thepair of multi-function electrodes 1214. Where this second pair ofelectrodes is used, the second ECG signals (and resulting data) benefitfrom increased reliability due to increased accuracy and precision ofconductive electrodes. In some examples, the act of receiving 1314 thesecond ECG data includes one or more of the acts described above withreference to the act 614.

Next, the treatment controller attempts to verify 616 the declaredarrhythmia using the second ECG data by executing an arrhythmiaverification process. In an example, the verification 616 of the secondECG data results in a more reliable determination of whether or not thepatient is experiencing an arrhythmia condition.

Where the treatment controller refutes or otherwise fails to verify 618the declared arrhythmia condition, the treatment controller aborts ordelays 620 the treatment protocol. Upon verifying 618 the arrhythmiadeclaration, the treatment controller delivers 622, in an attempt torestore a normal rhythm to the patient's heart, one or more therapeuticstimulation pulses as selected in response to the type of arrhythmiacondition detected. This verification 618 may occur during a period oftime in which treatment has been delayed 620 or may occur prior to anydelay 620 of treatment.

After delivery 622 of the therapy, the treatment controller analyzes thesecond ECG signals to determine 624 whether a “normal” heart rhythm(e.g., normal sinus rhythm) has been restored. If a normal rhythm hasbeen restored, the treatment controller returns control to the cardiacmonitor. However, if a normal rhythm has not been restored, thetreatment controller determines whether or not treatment should becontinued 626. If treatment can be continued 626, the treatment protocolmay optionally be adjusted 628 to, for example, change the type oftherapeutic stimulation pulse provided to the patient. If the treatmentcannot be continued 626, the monitoring and treatment process 1300 ends.

Some examples advantageously leverage the features disclosed above toprovide for an ambulatory medical treatment device that utilizesdistinct pairs of sensing electrodes and gel deployment in execution ofabnormality detection and arrhythmia verification processes. Examples ofthis ambulatory medical treatment device and the processes it executesare illustrated by FIGS. 14 and 15.

As shown, FIG. 14 includes a medical device 1400 that is external,ambulatory, and wearable by the patient 102. The medical device 1400includes the components of the medical device 100 described above. Forexample, the medical device 1400 includes the garment 110, the therapyelectrode pair 114, two pairs of sensing electrodes 112 a and 112 b, themedical device controller 120, the connection pod 130, the patientinterface pod 140, and the belt 150. Each of the electrodes isconfigured to couple externally to a skin of the patient 102. Thetherapy electrode pair 114 is also configured to provide one or moretherapeutic stimulation pulses to a heart of the patient 102 duringexecution of a treatment protocol. The therapy electrodes 114 areincluded within therapy pads that also house gel dispensers coupled toand under control of gel dispenser circuitry. This gel dispensercircuitry is coupled to and under control of a processor within themedical device controller 120. In addition, the medical device 1400includes the distinct sensing electrode pair 1012 described above withreference to FIG. 10.

In some examples, the medical device 1400 is configured to acquire firstECG signals via the sensing electrode pairs 112 and to acquire secondECG signals via the sensing electrode pair 1012. The sensing electrodepairs 112 may include, for example, dry electrodes. The sensingelectrode pair 1012 may include, for example, conductive electrodes. Insome examples, second ECG data based on the second ECG signals has animproved reliability over first ECG data based on the first ECG signals.

In some examples, the medical device controller 120 of the medicaldevice 1400 includes a cardiac monitor (e.g., the cardiac monitor 214)and a treatment controller (e.g., the treatment controller 216). Inthese examples, the cardiac monitor and treatment controller areconfigured to execute monitoring and treatment processes that includeabnormality detection and arrhythmia verification processes. At leastone example monitoring and treatment process 1500 that the cardiacmonitor and the treatment controller are configured to execute isdescribed further below with reference to FIG. 15.

As shown in FIG. 15, the monitoring and treatment process 1500 includesthe actions of the monitoring and treatment process 600. However, manyof the details of the monitoring and treatment process 600 are omittedfrom the following description of the monitoring and treatment process1500 for the sake of brevity. As shown in FIG. 15, the monitoring andtreatment process 1500 starts with the cardiac monitor receiving 1502first ECG data based on first ECG signals acquired by at least one firstpair of sensing electrodes. In this example, the at least one first pairof sensing electrodes includes the sensing electrode pairs 112. In someexamples, the act of receiving 1502 the first ECG data includes one ormore of the acts described above with reference to the act 602.

Next, the cardiac monitor attempts to detect abnormalities 604 in thefirst ECG data by executing an abnormality detection process asdescribed above. Where the cardiac monitor does not detect 606 anarrhythmia condition of the patient, the cardiac monitor returns toreceiving 1502 first ECG data. However, upon detecting 606 that thepatient is experiencing an arrhythmia condition, the cardiac monitorrecords 608 an initial arrhythmia declaration and initiates 610 atreatment protocol.

In one example, after initiation 610 of the treatment protocol, thetreatment controller controls, via a gel dispenser and associatedcircuitry, application 1512 of conductive gel between the patient's skinand a second pair of electrodes (e.g., the electrode pair 1012). Theconductive gel may be applied between the second pair of electrodes andthe skin of the patient prior to acquiring second ECG signals, asdescribed herein. In some examples, the act of applying 1512 theconductive gel includes one or more of the acts described above withreference to the act 612.

The monitoring and treatment process 1500 continues with the treatmentcontroller receiving 1514 second ECG data based on second ECG signalsacquired by the second pair of electrodes. In this example, the secondpair of electrodes is the pair of sensing electrodes 1012. Where thissecond pair of electrodes is used, the second ECG signals (and resultingdata) benefit from increased reliability due to increased accuracy andprecision of conductive sensing electrodes. In some examples, the act ofreceiving 1514 the second ECG data includes one or more of the actsdescribed above with reference to the act 614.

Next, the treatment controller attempts to verify 616 the declaredarrhythmia using the second ECG data by executing an arrhythmiaverification process. In an example, the verification 616 of the secondECG data results in a more reliable determination of whether or not thepatient is experiencing an arrhythmia condition.

Where the treatment controller refutes or otherwise fails to verify 618the declared arrhythmia condition, the treatment controller aborts ordelays 620 the treatment protocol. Upon verifying 618 the arrhythmiadeclaration, the treatment controller delivers 622, in an attempt torestore a normal rhythm to the patient's heart, one or more therapeuticstimulation pulses as selected in response to the type of arrhythmiacondition detected. This verification 618 may occur during a period oftime in which treatment has been delayed 620 or may occur prior to anydelay 620 of treatment.

After delivery 622 of the therapy, the treatment controller analyzes thesecond ECG signals to determine 624 whether a “normal” heart rhythm(i.e., not an arrhythmia condition) has been restored. If a normalrhythm has been restored, the treatment controller returns control tothe cardiac monitor. However, if a normal rhythm has not been restored,the treatment controller determines whether or not treatment should becontinued 626. If treatment can be continued 626, the treatment protocolmay optionally be adjusted 628 to, for example, change the type oftherapeutic stimulation pulse provided to the patient. If the treatmentcannot be continued 626, the monitoring and treatment process 1500 ends.

Some examples advantageously leverage the features disclosed above toprovide for an ambulatory medical treatment device that executesdistinct abnormality detection and arrhythmia verification processes.Examples of these ambulatory medical treatment devices and the processesthey execute are illustrated by FIGS. 16-19.

As shown, FIG. 16 includes a medical device 1600 that is external,ambulatory, and wearable by the patient 102. The medical device 1600includes many of the components of the medical device 100 describedabove. For example, the medical device 1600 includes the garment 110,the therapy electrode pair 114, the pairs of sensing electrodes 112, themedical device controller 120, the connection pod 130, the patientinterface pod 140, and the belt 150. Each of the electrodes isconfigured to couple externally to a skin of the patient 102. Thetherapy electrode pair 114 is also configured to provide one or moretherapeutic stimulation pulses to a heart of the patient 102 duringexecution of a treatment protocol. The sensing electrode pairs 112 areconfigured to couple externally to a skin of a patient and to acquireECG signals of the patient 102.

In some examples, the medical device 1600 is configured to acquire firstand second ECG signals via the sensing electrode pairs 112. The sensingelectrode pairs 112 may be, for example, dry electrodes. Regardless ofthe electrodes used to acquire the ECG signals, in some examples, themedical device 1600 includes ECG sensing electrode circuitry (e.g., asprovided by the sensor interface 212 and the at least one processor 218)that is configured to process first and second ECG data generated fromthe first and second ECG signals using distinct ECG analysis processes(i.e., an abnormality detection process and an arrhythmia verificationprocess). In these examples, the combination of the abnormalitydetection process and the arrhythmia verification process has animproved reliability over the abnormality detection process alone.

In some examples, the medical device controller 120 of the medicaldevice 1600 includes a cardiac monitor (e.g., the cardiac monitor 214)and a treatment controller (e.g., the treatment controller 216). Inthese examples, the cardiac monitor and treatment controller areconfigured to execute monitoring and treatment processes that includethe abnormality detection and arrhythmia verification processes. Atleast one example monitoring and treatment process 1700 that the cardiacmonitor and the treatment controller are configured to execute isdescribed further below with reference to FIG. 17.

As shown in FIG. 17, the monitoring and treatment process 1700 includesthe actions of the monitoring and treatment process 600. However, manyof the details of the monitoring and treatment process 600 are omittedfrom the following description of the monitoring and treatment process1700 for the sake of brevity. As illustrated in FIG. 17, the monitoringand treatment process 1700 starts with the cardiac monitor receiving1702 first ECG data based on first ECG signals acquired by at least onefirst pair of sensing electrodes. In this example, the at least onefirst pair of sensing electrodes includes the sensing electrode pairs112. In some examples, the act of receiving 1702 the first ECG dataincludes one or more of the acts described above with reference to theact 602.

Next, the cardiac monitor attempts to detect abnormalities 1704 in thefirst ECG data by executing an abnormality detection process asdescribed above. In some examples, the act of detecting 1704 anabnormality includes one or more of the acts described above withreference to the act 604. Where the cardiac monitor does not detect 606an arrhythmia condition of the patient, the cardiac monitor returns toreceiving 1702 first ECG data. However, upon detecting 606 that thepatient is experiencing an arrhythmia condition, the cardiac monitorrecords 608 an initial arrhythmia declaration and initiates 610 atreatment protocol. In some examples, the treatment protocol includesissuance 1706 of an alarm of an impending therapeutic stimulation pulse.

In one example, after initiation 610 of the treatment protocol, thetreatment controller controls, via a gel dispenser and associatedcircuitry, optional application 1712 of conductive gel between thepatient's skin and a second pair of electrodes (e.g., the therapyelectrode pair 114). The conductive gel may be applied between thesecond pair of electrodes and the skin of the patient prior to acquiringsecond ECG signals, as described herein. In some examples, the act ofapplying 1712 the conductive gel includes one or more of the actsdescribed above with reference to the act 612.

The monitoring and treatment process 1700 continues with the treatmentcontroller receiving 1714 second ECG data based on second ECG signalsacquired by the pair of sensing electrodes 112. In some examples, theact of receiving 1714 the second ECG data includes one or more of theacts described above with reference to the act 614.

In some examples, the second ECG signals are acquired over a predefinedperiod of time with a duration of between 5 and 10 seconds. In someexamples, the duration varies with the type of arrhythmia conditiondetected. For instance, where the arrhythmia condition detected isventricular tachycardia, the duration may span 8 to 10 seconds. However,where the arrhythmia condition detected is ventricular fibrillation, theduration may span 5 to 8 seconds.

Next, the treatment controller attempts to verify 1716 the declaredarrhythmia using the second ECG data by executing an arrhythmiaverification process. In an example, the verification 1716 of the secondECG data is accomplished by activating the ECG sensing electrodecircuitry to execute the arrhythmia verification process and executionof the arrhythmia verification process results in a more reliabledetermination of whether or not the patient is experiencing anarrhythmia condition. In some examples, the act of verifying 1716 anarrhythmia includes one or more of the acts described above withreference to the act 616.

Where the treatment controller fails to verify 618 the declaredarrhythmia condition, the treatment controller aborts or delays 620 thetreatment protocol. This delay may have a duration of at least 30seconds and, as shown in FIG. 17, the treatment controller may return toreceiving and processing second ECG data during the delay. In someexamples, in executing the arrhythmia verification process, thetreatment controller may determine a value that indicates a confidencethat the second ECG data reflects normal cardiac function of thepatient. In some examples, the treatment controller evaluates this value(e.g., by comparing it to a threshold value) to contribute to theverification of the arrhythmia condition.

As described above, in some examples, the abnormality detection processincludes a first set of sub-processes and the arrhythmia verificationprocess includes a second set of sub-processes. The first set mayinclude a number of sub-processes different from the second set. Forinstance, the first set may include more sub-processes than the secondset. In some examples, the second set of sub-processes includes a heartrate detection sub-process and/or a signal morphology detectionsub-process. In some examples, the first set of sub-processes includesan FFT and the second set of sub-processes omits the FFT. In otherexamples the first set of sub-processes and the second set ofsub-processes may include other sub-processes and the examples disclosedherein are not limited to a particular mapping of sub-processes to thefirst and second sets of sub-processes.

Upon verifying 618 the arrhythmia declaration, the treatment controllerdelivers 622, in an attempt to restore a normal rhythm to the patient'sheart, one or more therapeutic stimulation pulses as selected inresponse to the type of arrhythmia condition detected. This verification618 may occur during a period of time in which treatment has beendelayed 620 or may occur prior to any delay 620 of treatment.

After delivery 622 of the therapy, the treatment controller analyzes thesecond ECG signals to determine 624 whether a “normal” heart rhythm(i.e., not an arrhythmia condition) has been restored. If a normalrhythm has been restored, the treatment controller returns control tothe cardiac monitor. However, if a normal rhythm has not been restored,the treatment controller determines whether or not treatment should becontinued 626. If treatment can be continued 626, the treatment protocolmay optionally be adjusted 628 to, for example, change the type oftherapeutic stimulation pulse provided to the patient. If the treatmentcannot be continued 626, the monitoring and treatment process 1700 ends.

As shown, FIG. 18 includes a medical device 1800 that is external,ambulatory, and wearable by the patient 102. The medical device 1800includes many of the components of the medical device 100 describedabove. For example, the medical device 1800 includes the therapyelectrode pair 114 and the pairs of sensing electrodes 112, althoughonly one of the anterior/posterior sensing electrodes 112 a and theanterior therapy electrode 114 a are shown. Each of the electrodes isconfigured to couple externally to a skin of the patient 102. Thetherapy electrode pair 114 is also configured to provide one or moretherapeutic stimulation pulses to a heart of the patient 102 duringexecution of a treatment protocol. The sensing electrode pairs 112 areconfigured to couple externally to a skin of a patient and to acquireECG signals of the patient 102. In certain implementations as describedabove, the medical device 1800 can be configured to acquire the ECGsignals via the therapy electrodes 114 (e.g., configured as amulti-functional electrode) instead of or in addition to the sensingelectrodes 112. The medical device 1800 also includes the medical devicecontroller 120 and the connection pod 130. In addition, the medicaldevice 1800 includes a garment 1810 and tensioners 1820 a and 1820 b.

In some examples, the tensioners 1820 a and 1820 b include electricaland/or mechanical components configured to tighten and/or loosen thegarment 1810 around the patient. By tightening the garment 1810 aroundthe patient, the tensioners 1820 a and 1820 b increase the quality ofthe electrical coupling between the patient's skin and the pairs ofsensing electrodes 112, thereby improving the reliability of signalsacquired thereby while the garment 1810 is tightened.

In some examples, the tensioners 1820 a and 1820 b includeelectromechanical components under control of the medical devicecontroller 120, and more specifically, the processor 218 via sensorinterface 212. For instance, in some examples, the tensioners 1820 a and1820 b each include interior components like those of the electrodeassemblies illustrated in FIGS. 3d-3g of U.S. Pat. No. 4,928,690 titled“PORTABLE DEVICE FOR SENSING CARDIAC FUNCTION AND AUTOMATICALLYDELIVERING ELECTRICAL THERAPY,” which is hereby incorporated herein byreference in its entirety. In these examples, the processor 218 isconfigured to cause, as part of an arrhythmia verification process, thesensor interface 212 to electrically operate a release within theinterior components to tighten the garment 1810 around the patient. Thistightening improves reliability of signals acquired by the sensingelectrodes 112.

Alternatively or additionally, in some examples, the garment 1810includes tensile actuators composed of twist-spun nanofiber yarn and/ortwist-inserted polymer fibers that generate tensile actuation whenpowered electrically, such as those described in International PatentApplication Publication No. WO2014/022667, titled “COILED AND NON-COILEDTWISTED NANOFIBER YARN AND POLYMER FIBER TORSIONAL AND TENSILEACTUATORS,” which is hereby incorporated herein by reference in itsentirety. In these examples, the tensioners 1820 a and 1820 b eachinclude electrical contacts coupled to the tensile actuators. Further,in these examples, the medical device controller 120, and morespecifically, the processor 218 via the sensor interface 212, isconfigured to electrically power, as part of an arrhythmia verificationprocess, the tensile actuators via the electrical contacts to tightenthe garment 1810 around the patient. This tightening improvesreliability of signals acquired by the sensing electrodes 112. Otherexamples of the tensioners 1820 a and 1820 b may be included within themedical device 1800 without departing from the scope of this disclosure.

In some examples, the medical device 1800 is configured to acquire firstand second ECG signals via the sensing electrode pairs 112. The sensingelectrode pairs 112 may be, for example, dry electrodes. Regardless ofthe electrodes used to acquire the ECG signals, in some examples, themedical device 1800 is configured to acquire the first ECG signals whilethe garment 1810 is not tightened and to acquire the second ECG signalswhile the garment 1810 is tightened. Further, in some examples, themedical device 1800 includes ECG sensing electrode circuitry (e.g., asprovided by the sensor interface 212 and the at least one processor 218)that is configured to process first and second ECG data generated fromthe first and second ECG signals using distinct ECG analysis processes(i.e., an abnormality detection process and an arrhythmia verificationprocess). In these examples, the combination of the abnormalitydetection process and the arrhythmia verification process has animproved reliability over the abnormality detection process alone, dueat least in part to the higher quality electrical coupling created bytightening the garment 1810 around the patient.

In some examples, the medical device controller 120 of the medicaldevice 1800 includes a cardiac monitor (e.g., the cardiac monitor 214)and a treatment controller (e.g., the treatment controller 216). Inthese examples, the cardiac monitor and treatment controller areconfigured to execute monitoring and treatment processes that includethe abnormality detection and arrhythmia verification processes. Atleast one example monitoring and treatment process 1900 that the cardiacmonitor and the treatment controller are configured to execute isdescribed further below with reference to FIG. 19.

As shown in FIG. 19, the monitoring and treatment process 1900 includesthe actions of the monitoring and treatment process 600. However, manyof the details of the monitoring and treatment process 600 are omittedfrom the following description of the monitoring and treatment process1900 for the sake of brevity. As illustrated in FIG. 19, the monitoringand treatment process 1900 starts with the cardiac monitor receiving1902 first ECG data based on first ECG signals acquired by at least onefirst pair of sensing electrodes. In this example, the at least onefirst pair of sensing electrodes includes the sensing electrode pairs112. In some examples, the act of receiving 1902 the first ECG dataincludes one or more of the acts described above with reference to theact 602.

Next, the cardiac monitor attempts to detect abnormalities 1904 in thefirst ECG data by executing an abnormality detection process asdescribed above. In some examples, the act of detecting 1904 anabnormality includes one or more of the acts described above withreference to the act 604. Where the cardiac monitor does not detect 606an arrhythmia condition of the patient, the cardiac monitor returns toreceiving 1902 first ECG data. However, upon detecting 606 that thepatient is experiencing an arrhythmia condition, the cardiac monitorrecords 608 an initial arrhythmia declaration and initiates 610 atreatment protocol. In some examples, the treatment protocol includesissuance 1906 of an alarm of an impending therapeutic stimulation pulse.

In one example, after initiation 610 of the treatment protocol, thetreatment controller controls, via a gel dispenser and associatedcircuitry, optional application 1912 of conductive gel between thepatient's skin and the first pair of electrodes. The conductive gel maybe applied between the first pair of electrodes and the skin of thepatient prior to acquiring second ECG signals, as described herein. Insome examples, the act of applying 1912 the conductive gel includes oneor more of the acts described above with reference to the act 612. Insome examples, the act 1912 of applying the conductive gel may becarried out after the verification of the arrhythmia in act 618.

In act 1913, the treatment controller controls one or more tensioners(e.g., the tensioners 1820 a and 1820 b), via associated circuitry(e.g., the sensor interface 212), to tighten a garment (e.g., thegarment 1810) around the patient. For instance, the treatment controllermay transmit (via the sensor interface) a control signal to the one ormore tensioners to operate a release to apply tension to the garmentand/or transmit a control signal to the one or more tensioners to powertensile actuators within the garment.

The monitoring and treatment process 1900 continues with the treatmentcontroller receiving 1914 second ECG data based on second ECG signalsacquired by the pair of sensing electrodes 112. In some examples, theact of receiving 1914 the second ECG data includes one or more of theacts described above with reference to the act 614.

In some examples, the second ECG signals are acquired over a predefinedperiod of time with a duration of between 5 and 10 seconds. In someexamples, the duration varies with the type of arrhythmia conditiondetected. For instance, where the arrhythmia condition detected isventricular tachycardia, the duration may span 8 to 10 seconds. However,where the arrhythmia condition detected is ventricular fibrillation, theduration may span 5 to 8 seconds.

Next, the treatment controller attempts to verify 1916 the declaredarrhythmia using the second ECG data by executing an arrhythmiaverification process. In examples, the acts 1913, 1914 and 1916 can betogether considered part of the arrhythmia verification process. Theverification 1916 of the initial declaration of the arrhythmia based onthe second ECG data can be accomplished by activating the ECG sensingelectrode circuitry to execute the arrhythmia verification process.Execution of the arrhythmia verification process results in a morereliable determination of whether or not the patient is experiencing anarrhythmia condition. In some examples, the act of verifying 1916 anarrhythmia includes one or more of the acts described above withreference to the act 616 (see FIG. 6A and the example processes andsub-processes described in Table 1).

Where the treatment controller refutes or otherwise fails to verify 618the declared arrhythmia condition, the treatment controller aborts ordelays 620 the treatment protocol. This delay may have a duration of atleast 30 to 45 seconds and, as shown in FIG. 19, the treatmentcontroller may return to receiving and processing second ECG data duringthe delay. If via execution of the act 618 or during the delay period,the treatment controller determines that normal sinus rhythm hasreturned in the patient, the treatment protocol can be aborted and themedical device can return to a monitoring state via the cardiac monitor.In some examples, in executing the arrhythmia verification process, thetreatment controller may determine a value that indicates a confidencethat the second ECG data reflects normal cardiac function of thepatient. In some examples, the treatment controller evaluates this value(e.g., by comparing it to a threshold value) to contribute to theverification of the arrhythmia condition.

As described above, in some examples, the abnormality detection processincludes a first set of sub-processes and the arrhythmia verificationprocess includes a second set of sub-processes. The first set mayinclude a number of sub-processes different from the second set. Forinstance, the first set may include more sub-processes than the secondset. In some examples, the second set of sub-processes includes a heartrate detection sub-process and/or a signal morphology detectionsub-process. In some examples, the first set of sub-processes includesan FFT and the second set of sub-processes omits the FFT. In otherexamples the first set of sub-processes and the second set ofsub-processes may include other sub-processes and the examples disclosedherein are not limited to a particular mapping of sub-processes to thefirst and second sets of sub-processes. Alternatively or additionally,in some examples, the first set of sub-processes and the second set ofsub-processes may be identical, but, in these examples, the arrhythmiaverification process may still provide improved reliability by virtue ofthe signals acquired while the garment is tightened around the patient.

Upon verifying 618 the arrhythmia declaration, the treatment controllerdelivers 622, in an attempt to restore a normal rhythm to the patient'sheart, one or more therapeutic stimulation pulses as selected inresponse to the type of arrhythmia condition detected. This verification618 may occur during a period of time in which treatment has beendelayed 620 or may occur prior to any delay 620 of treatment.

After delivery 622 of the therapy, the treatment controller analyzes thesecond ECG signals to determine 624 whether a “normal” heart rhythm(e.g., a normal sinus rhythm) has been restored. If a normal rhythm hasbeen restored, the treatment controller returns control to the cardiacmonitor. However, if a normal rhythm has not been restored, thetreatment controller determines whether or not treatment should becontinued 626. If treatment can be continued 626, the treatment protocolmay optionally be adjusted 628 to, for example, change the type oftherapeutic stimulation pulse provided to the patient. If the treatmentcannot be continued 626, the monitoring and treatment process 1900 ends.

Further Considerations

Although the subject matter contained herein has been described indetail for the purpose of illustration, it is to be understood that suchdetail is solely for that purpose and that the present disclosure is notlimited to the disclosed examples, but, on the contrary, is intended tocover modifications and equivalent arrangements that are within thescope of the appended claims. For example, it is to be understood thatthe present disclosure contemplates that, to the extent possible, one ormore features of any example can be combined with one or more featuresof any other example.

Other examples are within the scope of the description and claims.Additionally, certain functions described above can be implemented usingsoftware, hardware, firmware, hardwiring, or combinations of any ofthese. Features implementing functions can also be physically located atvarious positions, including being distributed such that portions offunctions are implemented at different physical locations. cm 1-11.(canceled)

12. An ambulatory medical device comprising: a pair of sensingelectrodes configured to couple externally to a skin of a patient and toacquire first electrocardiogram (ECG) signals to detect an arrhythmiacondition of the patient; a pair of multi-function electrodes configuredto couple externally to the skin of the patient and to provide one ormore therapeutic stimulation pulses to a heart of the patient duringexecution of a treatment protocol and to acquire second ECG signals toverify the arrhythmia condition of the patient; and at least oneprocessor coupled to the pair of sensing electrodes and the pair ofmulti-function electrodes and configured to receive first ECG datagenerated from the first ECG signals; analyze the first ECG data todetect the arrhythmia condition of the patient using an abnormalitydetection process; record an initial declaration of the arrhythmiacondition of the patient in response to detecting the arrhythmiacondition; initiate the treatment protocol in response to the initialdeclaration; receive second ECG data generated from the second ECGsignals; and analyze the second ECG data to either verify or refute theinitial declaration of the arrhythmia condition using an arrhythmiaverification process distinct from the abnormality detection process.13. The ambulatory medical device of claim 12, wherein the at least oneprocessor is further configured to delay the treatment protocol inresponse to refuting the initial declaration of the arrhythmiacondition.
 14. The ambulatory medical device of claim 12, wherein the atleast one processor is further configured to abort the treatmentprotocol in response to determining that normal rhythm has returned inthe patient.
 15. The ambulatory medical device of claim 12, wherein theat least one processor is further configured to control delivery of theone or more therapeutic stimulation pulses to the heart of the patientin response to verifying the initial declaration of the arrhythmiacondition.
 16. The ambulatory medical device of claim 12, furthercomprising gel deployment circuitry coupled to the at least oneprocessor, wherein the at least one processor is further configured tosignal the gel deployment circuitry to cause at least one gel dispenserto apply conductive gel between the skin of the patient and the pair ofmulti-function electrodes in response to detecting the arrhythmiacondition and prior to acquiring the second ECG signals.
 17. Theambulatory medical device of claim 16, further comprising a pair ofelectrode assemblies comprising the pair of multi-function electrodesand the at least one gel dispenser.
 18. The ambulatory medical device ofclaim 16, further comprising a pair of therapy pads comprising the atleast one gel dispenser and a pair of therapy electrodes, wherein thepair of multi-function electrodes comprise the pair of therapyelectrodes.
 19. The ambulatory medical device of claim 18, furthercomprising at least one non-ECG sensor, the at least one non-ECG sensorcomprising one or more of an accelerometer and a photoplethysmographsensor, wherein the at least one processor is further coupled to the atleast one non-ECG sensor and is further configured to: receive non-ECGdata generated from signals acquired by the at least one non-ECG sensor;and analyze the non-ECG data using the abnormality detection process tocontribute to detection of the arrhythmia condition. 20-22. (canceled)23. An ambulatory medical device comprising: a pair of therapyelectrodes configured to couple externally to a skin of a patient and toprovide at least one therapeutic stimulation pulse to a heart of thepatient; a pair of sensing electrodes configured to couple externally tothe skin of the patient and to acquire first and second ofelectrocardiogram (ECG) signals from the patient; ECG sensing electrodecircuitry coupled to the pair of sensing electrodes and configured toprocess the acquired first and second ECG signals from the patient togenerate first and second ECG data; and at least one processor coupledto the pair of sensing electrodes, the ECG sensing electrode circuitry,and the pair of therapy electrodes and configured to receive the firstECG data; analyze the first ECG data using a first process to detect anarrhythmia condition of the patient, wherein the first process comprisesan abnormality detection process; record an initial declaration of thearrhythmia condition of the patient in response to detecting thearrhythmia condition; initiate a treatment protocol in response to theinitial declaration of the arrhythmia condition, the treatment protocolspecifying provision of at least one alarm indicating an imminentdelivery of the at least one therapeutic stimulation pulse and provisionof the at least one therapeutic stimulation pulse; cause the ECG sensingelectrode circuitry to activate a second process distinct from the firstprocess to analyze the second ECG signals, wherein the second processcomprises an arrhythmia verification process; receive the second ECGdata; and analyze, after the provision of the at least one alarm andbefore the provision of the at least one therapeutic stimulation pulse,the second ECG data using the second process distinct from the firstprocess to verify the initial declaration of the arrhythmia condition.24. (canceled)
 25. The ambulatory medical device of claim 23, whereinthe at least one processor is further configured to control delivery ofthe at least one therapeutic stimulation pulse in response to verifyingthe initial declaration of the arrhythmia condition.
 26. The ambulatorymedical device of claim 23, wherein the at least one processor isfurther configured to: refute, using the second ECG data, the initialdeclaration of the arrhythmia condition; and delay the provision of theat least one therapeutic stimulation pulse in response to refuting theinitial declaration of the arrhythmia condition.
 27. The ambulatorymedical device of claim 26, wherein the delay comprises a delay having aduration between 30 seconds and 45 seconds. 28-30. (canceled)
 31. Theambulatory medical device of claim 23, wherein the abnormality detectionprocess comprises a first number of sub-processes and the arrhythmiaverification process comprises a second number of sub-processes lessthan the first number of sub-processes.
 32. The ambulatory medicaldevice of claim 23, wherein the abnormality detection process comprisesa first set of sub-processes and the arrhythmia verification processcomprises a second set of sub-processes different than the first set ofsub-processes.
 33. The ambulatory medical device of claim 23, whereinthe arrhythmia verification process comprises at least one of a heartrate detection sub-process and a signal morphology detectionsub-process.
 34. The ambulatory medical device of claim 33, wherein theabnormality detection process comprises a first fast Fourier transformand the arrhythmia verification process omits a second fast Fouriertransform.
 35. The ambulatory medical device of claim 23, wherein the atleast one processor is configured to cause the ECG sensing electrodecircuitry to activate the second process to analyze the second ECGsignals within-ef a predefined period of time after the initialdeclaration of the arrhythmia condition.
 36. The ambulatory medicaldevice of claim 35, wherein the predefined period of time comprises arange from between 1 to 60 seconds.
 37. (canceled)
 38. The ambulatorymedical device of claim 35, wherein the arrhythmia condition isventricular tachycardia or ventricular fibrillation, and the predefinedperiod of time comprises a range from between 5 to 10 seconds. 39.(canceled)
 40. The ambulatory medical device of claim 23, furthercomprising at least one non-ECG sensor, the at least one non-ECG sensorcomprising an accelerometer, wherein the at least one processor isfurther coupled to the at least one non-ECG sensor and is furtherconfigured to: receive non-ECG data generated from signals acquired bythe at least one non-ECG sensor; and analyze the non-ECG data with theabnormality detection process to contribute to detection of thearrhythmia condition.
 41. (canceled)